Specimens Of Different Thickness Research Articles

A new method for predicting reference temperature of ferritic steel using finite element analysis and master curve method

Fracture toughness is an important parameter for measuring material properties in industry. In order to obtain data on the fracture toughness of a material it is often necessary to carry out a large number of fracture toughness experiments. The cost of the experiments is high and the experimental process is cumbersome. Moreover, in practice, there are often not a large number of materials that meet the requirements for the experiment. The relationship between different experimental ambient temperatures and fracture toughness can be determined by determining the reference temperature T0 in the master curve method. In this paper the load-displacement curves of the specimens are obtained using finite element analysis. Determine the J integrals corresponding to the initiating load Pint and the maximum load Pc on the load-displacement curve using the Load Slope Compliance Changing Rate method. Determine the reference temperature T0 in conjunction with the single temperature method. On the one hand, in order to validate the method, finite element analyses were performed on specimens of different thicknesses, temperatures, materials and types. This method was also applied to obtain fracture toughness data and to determine the reference temperature T0. On the other hand, combining the master curve method and combining the experimental data of 16MnDR, 16MnR and 20MnMoNi55 ferritic steels were verified. The experimental results show that the results predicted by this method are in good agreement with the actual results. However, it has a certain conservative type. It provides a good solution for practical engineering. The accuracy of fracture toughness and reference temperature of ferritic steels of different thicknesses can be verified by few experiments.

Methodology for the mechanical characterisation of hyperelastic adhesives. Experimental validation on joints of different thicknesses

This work focuses on the mechanical characterisation of adhesives with hyperelastic behaviour and on the determination of the behavioural laws that best represent it, in order to introduce them in simulation models. First, a test plan is carried out on simple specimens: uniaxial and planar configuration. These are designed to measure the non-linear behaviour of adhesives in both tensile and pure shear. Unlike the uniaxial specimen, which is governed by a test standard (UNE-ISO 37) that defines its geometry, the planar specimen does not have a standard that defines its dimensions. Therefore, in this research it is proposed to carry out tests with specimens of different width-length sizes to evaluate how these dimensions affect the stress-strain curves.For mechanical characterisation, finite element programs provide the tool to evaluate the predicted behaviour of a hyperelastic material from the experimental results, displaying in the same graph the degree of approximation obtained for the results of each test (Dumbbell and planar) with different hyperelastic models, allowing us to select the hyperelastic model that best fits the experimental data.The Mooney-Rivlin model was found to be the best fitting model and therefore the most appropriate to describe the behaviour of hyperelastic adhesives used in this study. To conclude this study, the obtained law was validated by comparing the results of tests carried out on single lap joint (SLJ) specimens of different thickness.

Size-dependence of AM Ti–6Al–4V: Experimental characterization and applications in thin-walled structures simulations

Previous studies show that the properties of parts manufactured via additive manufacturing, such as selective laser melting, depend on local feature sizes like lattice wall thickness and strut diameter. Although size dependence has been studied extensively, it was not included in constitutive models for numerical simulations. In this work, flat dog-bone tensile specimens of different thicknesses were manufactured and tested under quasi-static conditions to characterize the size-dependent properties experimentally. It was observed that key mechanical properties decrease with specimen thickness. Through curve-fitting to experimental data, this work provides approximate analytical expressions for the material properties values as a function of specimen thickness, furnishing a phenomenological size-dependent constitutive model. The interpolating capability of the model is cross-validated with existing experimental data. Two numerical examples demonstrate the application of the size-dependent material model. The axial crushing of thin-walled lattices at varying wall thicknesses was simulated by the size-dependent material model and one that ignores size effects. Results show that ignoring size effects leads to overestimated peak crushing force and specific energy absorption. The two material models were also compared in the topology optimization of thin-walled structures. Results show that the size-dependent model leads to a more robust optimized design: having higher energy absorption and sustaining less material fracture.

Improvement of Nodularity Value of Graphite in Ductile Iron and Its Effect on Mechanical Properties

AbstractDuctile iron is becoming popular in many industrial applications due to its comparatively high strength and a considerable amount of ductility, which is because of the presence of spheroidal graphite in the microstructure. An effort has been made to improve the nodularity value of graphite in ductile iron by varying the fineness of inoculant, that is, ferro‐silicon (Fe‐Si) and section thickness of the casting. Further, the effects on mechanical properties are also studied. The spheroidal graphite iron specimens for different inoculant treatments, such as without any inoculation, in‐mold inoculation with coarse, and fine Fe‐Si, are prepared. The results have shown that the nodularity increased with in‐mold inoculation with Fe‐Si, and for the same amount of inoculated Fe‐Si, the nodularity is higher for fine Fe‐Si. Ultimate tensile strength is also found to increase with the increase in nodularity, and maximum strength of ≈460 MPa is recorded for a specimen having in‐mold inoculation with fine Fe‐Si. Stepped bar specimens of different thicknesses are also prepared by casting with the same composition for studying the effect of section thickness, and nodularity value is found to be higher for the thinnest section and is about ≈48%.

Thickness Effects on Oxidation Behavior and Consequent γ’ Degradation of a High-Al Ni-Based Single Crystal Superalloy

High temperature oxidation is considered to play an essential role in the thickness debit effect on the creep rupture life of Ni-based single crystal (SC) superalloys. In order to clarify thickness effects, thin-walled specimens of different thickness (t = 0.1, 0.3, 1.0 mm) were prepared. Cyclic and isothermal oxidation tests of a high-Al Ni-based SC superalloy IC21 were carried out at 900 °C and 1100 °C in order to study the thickness effects on the oxidation behavior and consequent microstructural degradation. Thin-walled specimens of S01-N exhibited a good oxidation resistance when the protective scale-forming elements were enough in the matrix. Specimen thickness tuned the oxidation kinetics by changing the spallation behavior but had few influences on the thermodynamics. The easier stress relief via creep deformation in thin specimens is the main reason behind this phenomenon. Moreover, the obvious temperature effects on the multilayer oxide scales caused the different thickness-related spallation behaviors. Weaker microstructural degradation appeared and was further mitigated by reduced specimen thickness. Sufficient Al content is considered to be indispensable for the formation of protective α-Al2O3 scale with less degradation of matrix during the high temperature oxidation of thin-walled Ni-based SC superalloy castings.

Matrix and fabric contribution on the tensile behaviour of fabric reinforced cementitious matrix composites

Fabric reinforced cementitious matrix (FRCM) are a type of sustainable materials for structures strengthening and envisaging to develop new construction solutions. However, the wide range of possible combinations of fabric and cementitious matrixes makes it necessary to study the particular contribution of mortar and fabric in the composite action of the FRCM. In this line, this study presents the experimental, analytical and numerical evaluation of the tensile behaviour of FRCM composites. 85 FRCM specimens of different thicknesses were manufactured, with one or two embedded fabrics of different type of fibres and geometry. Fabrics made of coated vegetal fibres were also considered to be compared with commercial fabrics of coated synthetic fibres. The results show a significant increase of the ultimate tensile strength with the increase of the FRCM thickness due to a residual contribution of the mortar after the cracking stage. The analytical model was effective for the cases that showed a cracking stabilization stage. However, the numerical model allows a closer approximation to experimental results because of considering the mortar contribution in the post-cracking stage.

Experimental investigation of wire arc additively manufactured steel single-lap shear bolted connections

An experimental investigation into the structural performance of wire arc additively manufactured (WAAM) steel single-lap shear bolted connections is presented in this paper. The steel wire had a nominal yield stress of 420 MPa. Sixty specimens of different thicknesses, printing strategies and geometric features including end distances and plate widths were tested and analysed. The shear-out, net section tension fracture, localised tearing and curl-bearing failure modes were observed and discussed, while end-splitting was also evident. Digital image correlation (DIC) was used for detailed monitoring and visualisation of the surface strain fields that developed during testing, providing valuable insight into the developed failure mechanisms. The experimental results, which generally followed the anticipated trends, were used to assess the applicability of current design specifications developed for conventional steel bolted connections to WAAM steel bolted connections. It was found that both the cold-formed steel specifications (AISI S100 and AS/NZS 4600) and the structural steel specifications (AISC 360 and EN 1993-1) devised for conventionally manufactured steel elements, could yield considerable overestimations and underestimations of the test capacities, depending on the geometry. The overestimations are caused by shortcomings in the existing design provisions for out-of-plane failure modes, which are particularly prevalent among WAAM steel connections due to their material ductility and surface undulations, which promote curling. The underestimations relate primarily to the conservatism of the shear-out provisions. Further research is underway to underpin the development of improved design provisions.

Structural Response of Wire Arc Additively Manufactured Steel Bolted Connections under Single Shear

AbstractAn experimental investigation into the structural performance of wire arc additively manufactured (WAAM) steel single‐lap shear bolted connections is presented in this paper. Sixty specimens of different thicknesses, printing strategies and geometric features, including end distances and plate widths, were manufactured using steel wire of a nominal yield strength of 420 MPa and subjected to single shear lap tests. The test results are analysed while the observed failure modes, featuring shear‐out, net section tension fracture, end‐splitting, localised tearing and curl‐bearing failure, are discussed. Digital image correlation (DIC) was used for detailed monitoring and visualisation of the surface strain fields that developed during testing, providing valuable insight into the developed failure mechanisms. The experimental results, which generally followed the anticipated trends, were used to assess the applicability of current design specifications developed for conventional steel bolted connections to WAAM steel bolted connections. It was found that both the cold‐formed steel specifications (AISI S100 and AS/NZS 4600) and the structural steel specifications (AISC 360 and EN 1993‐1) yield considerable overestimations or underestimations of the test capacities, depending on the specimen geometry. Further research is underway to underpin the development of improved design provisions.

Using Kubelka-Munk reflectance theory to predict optimal pink composite thickness and shade with an opaqued PEEK background for a final gingival color: An in vitro study

ObjectivesThe aims of this study were to demonstrate and evaluate how Kubelka-Munk (K-M) reflectance theory is used to adjust the color of the opaqued PEEK backing and the color and thickness of the resin composite layers in different thicknesses in order to minimize the color difference from a target gingival color. MethodsPEEK specimens were opaqued with either a dark or a light opaquer. Composite resin layers in 3 different colors were fabricated in varying thicknesses. Reflectance of opaqued PEEK and composite layers was determined using a spectroradiometer. Kubelka–Munk (K-M) absorption (K) and scattering (S) coefficients were derived for each material and then K-M reflectance theory was then used to predict the reflectance of each composite disk as layered on each backing. The color of the opaqued PEEK backings alone and the color of 12 pink composite layers on opaqued PEEK backings was calculated for the CIE D65 Illuminant. Composite resins in 3 different color were then bonded to the opaqued PEEK specimens and color differences of these specimens from the theoretical colors were determined. ResultsThe ∆E00 values ranged from 0.45 to 1.29 units for the bonded pink specimens and the K-M theory. K-M theory was validated as a viable predictor of gingival color using pink composite bonded to opaqued PEEK background. SignificanceUsing K-M theory to predict the gingival color of pink composite bonded to opaqued PEEK eliminates the need to make many specimens of different thicknesses that would otherwise be required to find an acceptable color match.

Experimental Analysis of Surface Defects in Electric Arc Welding Joints with Coated Electrode by Penetrant Test on Different Thicknesses

Welding is considered today as the standard joining operation in steel construction. Its purpose is to ensure the continuity of the material to be assembled, the quality of which depends on the proper functioning of the welding technique. Penetrant testing is a non-destructive test that consists of implementing investigative techniques to judge "without destruction" the state of the weld joint. The final objective of this work is to develop an opinion on the suitability of the welding joint of different thicknesses. Thus, metal specimens of different thicknesses were inspected. The results obtained show that, for small thicknesses, the defects are minimal and increase considerably, proportionally with an increase in the thickness of the welded parts. This analysis can be a way to facilitate the location of surface defects in order to reduce defects during welding operations.

Evaluation of the effect of anodization-colored titanium abutments and zirconia substructure thickness on zirconia substructure color: An In vitro study.

The aim of this study is to evaluate the effect of anodized titanium abutments and zirconia substructure thickness on the color of zirconia substructure. In this study, an electrochemical anodization setup was prepared for titanium coloring. Commercial titanium, anodization-colored yellow and pink titanium, and zirconia were used as different abutment specimens. Thirty zirconia discs in 0.7, 0.9, and 1.1 mm thickness were prepared from zirconia blocks as zirconia substructure specimens (n = 10). Zirconia substructure specimens of different thicknesses were placed on abutment specimens of different colors and L*, a*, b* values were measured with a spectrophotometer device. Color difference (ΔE) was calculated according to the CIELab formula by comparing the L*, a*, and b* values obtained on the zirconia abutment with the L*, a*, and b* values obtained on the other abutments. Statistical analyzes were performed with two-way analysis of variance and Tukey Honestly Significant Difference (HSD)test (p < 0.05). The increase in the thickness of the substructure resulted in a statistically significant difference on ΔE, L*, a*, and b* values (p < 0.001). The effect of abutment color had no significant effect on ΔE values. The highest ΔE value was 18.10 at zirconia substructure with 0.7 mm thickness when paired with pink-anodized titanium abutment specimens. The thickness of zirconia substructure and the color of titanium abutments affect zirconia substructure color.

Modeling of the fatigue crack growth of nickel-based superalloy using a constraint-based approach considering thickness

Varying thickness configurations have been applied to aero-engine turbine components. As a result, the thickness effect on the crack behavior must be considered in the damage tolerance method. The thickness effect remains a topic of discussion and needs further investigation due to limited studies on nickel-based superalloys. This study develops a fatigue crack growth (FCG) model which considers the thickness effect of nickel-based superalloy GH4169. FCG experiments were performed with specimens of different thicknesses at different temperatures. The results indicate that thickness significantly affects the FCG of GH4169, and the thickness effect is strongly temperature-dependent. A constraint-based model was employed to describe FCG with different thicknesses, emphasizing the influence of the stress state induced by the specimen thickness. Although this model works at room temperature, it fails to describe the crack growth at elevated temperatures. Therefore, a modified model was proposed to consider different temperatures. Successful predictions using the modified model can be achieved for different temperatures. This study offers new insights on quantifying the thickness effect on FCG of nickel-based superalloys.

Polyethylene swelling in organic solvents and its influence on mechanical properties

The results of kinetic investigations of the orthodichlorbenzene and orthoxylene sorption by the high density polyethylene specimens of different thickness for 35 days are presented. It is shown that the sorption of solvents results in swelling of the polymer and its plasticization, which is expressed in changes in its mechanical characteristics such as ultimate strength, deformation to failure, and Young's modulus.

Influence of Thickness and Shade on the Color of Layered Novel Nanohybrid Composite Systems.

The influence of the layer thickness and composite shade on the final color of Ceram.X composites (Dentsply Sirona) was tested, selecting five intermediate-translucency Ceram.X Universal shades, three high-translucency Ceram.X Duo "enamel" shades, and four low-translucency Ceram.X Duo "dentin" shades. Using cylindrical molds, 850 specimens were obtained, representing the whole array of possible Universal single specimens (in seven thicknesses, ranging from 1.0 to 4.0 mm in 0.5-mm increments) and Duo combinations. The CIELAB coordinates of each specimen were determined with a spectrophotometer. Different thicknesses and composites were compared with Clark's ΔE. The difference in color among specimens of different thicknesses was material-dependent. The thickness and shade of the composite markedly affected the color yield of the Ceram.X system. For each shade of the Universal systems, only one Duo enamel-dentin combination corresponded.

Investigation of The Size Effect of Self-Compacting Concrete on Direct Tensile Strength

The correct determination of direct tensile strength is very important in reinforced concrete building design. Unless otherwise specified in the building codes, the tensile strength that should be used in building design is direct tensile strength. However, the direct tensile strengths stated in the codes are usually found by formulas based on compressive strength, flexural tensile strength or splitting tensile strength. The fact that direct tensile tests are difficult to apply and there are no clear principles in the building codes, as in indirect methods, have led to a limited number of studies on direct tensile strength. In previous studies on direct tensile tests, certain standards were not established regarding the sizes and shapes of the samples subjected to the test. In this study, the size effect of self-compacting concrete (SCC) on direct tensile strength was investigated. In this context, direct tensile strengths of dog-bone type SCC specimens of different thicknesses were compared. The experimental direct tensile strengths were compared with the experimental splitting and flexural tensile strength, and also their proximity to tensile strengths expressed in certain building codes such as TS500, Eurocode and ACI 318 were investigated. As a result of the study, it was revealed that there is an inverse proportion between the thickness of the specimen and the direct tensile strength, and depending on the increase in the specimen thickness, the experimental direct tensile strengths approached the tensile strengths specified in the building codes.

Plasma treatment of spruce wood changes its dielectric properties

The effects of dielectric barrier discharge (DBD) plasma treatment on the dielectric properties of Norway spruce wood (Picea abies (L.) Karst.) were investigated using dielectric analysis. Dielectric constant (i.e. permittivity) and loss coefficient were determined at various frequencies. The resulting changes on lamellae specimens of different thicknesses were compared with the change in mass and moisture content. A significant influence of the plasma was found, leading to an increase of the dielectric constant by about 2%, and a decrease of sample mass directly after the plasma treatment by approx. 14%, whereas a reduction in moisture content by only about 0.6% and a corresponding change in loss coefficient were detected. Overall, the mechanisms of the observed changes remain unclear and seem mainly uncorrelated with the hitherto known chemical changes in wood surfaces caused by similar plasma discharges.

Modelling the Constraint Effect on Reference Temperature with Finite Element Parameters for Reactor Pressure Vessel Material 20MnMoNi55 Steel

A series of experiments were performed in the ductile to brittle transition region on three-point bending specimens of different thicknesses and a/W ratio of 20MnMoNi55 steel. master curve and reference temperature (T0) are obtained as per ASTM E1921-02 with different thickness and a/W ratio of the specimen and a variation of T0 is obtained, which indicates constant dependent on T0. Mathematic models are formulated to correlate T0 with Q-stress, T-stress and Triaxiality ratio to count for the constraint loss. Both the average value and also the maximum value of the finite element parameters are considered to predict T0 at different constraint label and compared with the experimental results.

Optical and mechanical factors in the temporal development of tooth–composite bond

ObjectivesTo obtain an accurate picture of the temporal development of bond strength between resin composites and tooth structures during cure for assessing debonding at the tooth–composite interface. MethodsAn assembly of uncured composite sandwiched between a glass block and a dentin slab with a layer of pre-cured adhesive was used in this study. A conventional composite was compared against a bulk-fill composite. The rate of bond formation was determined by measuring the tensile bond strength of specimens of different thicknesses at different time points during cure. The changing light irradiance exiting the composite as it cured was also recorded. Mode of fracture was analyzed by examining the fracture surfaces. ResultsPhoto-bleaching occurred in both resin composites. The development of the dentin–composite bond strength was initially dictated by the developing cohesive strength of the resin composite, and its final value was capped by the strength of the preformed dentin–adhesive bond. The higher interfacial irradiance in the bulk-fill composite did not lead to faster development of the overall bond strength. This was caused by its slower rate of cohesive strength development as reflected in the longer time for its interfacial irradiance to plateau and the greater proportion of cohesive failure seen in the initial stage of polymerization. The law of reciprocity did not hold for the development of dentin bond strength. SignificanceThe results from this study, when compared with the development of shrinkage stress, can be used as a basis for ensuring the integrity of the dentin–composite interface during cure.

Effect of Thickness on Fracture Toughness of Al6061-Graphite

This research work presents the study on fracture behavior of Al6061 with graphite particulate composite produced by the stir casting technique. The materials selected for the proposed work is Al6061 and graphite particles. Compact tension (CT) specimens were utilized to determine fracture toughness for different thickness of composite. In the present work, optimizing the parameters of the compact tension specimens is carried out using Taguchi method. Four parameters and two factors are considered to optimize the parameters. Factors considered are material composition and a/W ratio. From the Taguchi analysis, on compact tension specimens, Al6061-9%graphite is the optimized composition and fracture toughness is maximum for a/W ratio = 0.45. All the compact tension specimens of different thickness (B = 4, 5, 7, 10, 12, 15, 18 and 20mm) of a/W=0.45 were tested to find the fracture toughness. From the results, it was observed that the Kq reduces with increment in thickness to width (B/W) proportions and found to stay consistent for B/W≥0.3. This consistent estimation of Kq for B/W≥0.3 prevail the plane strain fracture toughness (KIc) of the composite.

Strength and Fracture Toughness of Hardox-400 Steel

This paper presents results of strength and fracture toughness properties of low-carbon high-strength Hardox-400 steel. Experimental tests were carried out for specimens of different thickness at wide temperature range from −100 to 20 °C. The dependences of the characteristic of material strength and fracture toughness on temperature based on experimental data are shown. Numerical calculation of the stress and strain distributions in area before crack tip using the finite element method (FEM) was done. Based on results of numerical calculation and observation of the fracture surfaces by scanning electron microscope (SEM), the critical local stress level at which brittle fracture takes place was assessed. Consideration of the levels of stress and strain in the analysis of the metal state at the tip of the crack allowed to justify the occurrence of the brittle-to-ductile fracture mechanism. On the basis of the results of stretch zone width measurements and stress components, the values of fracture toughness at the moment of crack initiation were calculated.