Effect Of Specimen Shape Research Articles

Effect of specimen shape on microbubble filling cleaning

Effect of specimen shape on microbubble filling cleaning

Cracking of granitic rock by high frequency-high voltage-alternating current actuation of piezoelectric properties of quartz mineral: 3D numerical study

This paper presents a numerical study on cracking of granitic rock by high frequency-high voltage-alternating current actuation (HF-HV-AC) of piezoelectric properties of Quartz mineral. For this end, a numerical method based on 3D embedded discontinuity finite elements for rock fracture and an explicit time stepping scheme to solve the coupled piezoelectro-mechanical problem is developed. Rock heterogeneity and anisotropy are accounted for at the mineral mesotructure level. Novel numerical simulations demonstrate that disc-shaped and cylindrical granitic rock specimens (with the tensile strength of about 8 MPa) can be cracked by a sinusoidal excitation with an amplitude of ∼10 kV at a frequency matching one of the resonance frequencies of the specimen (e.g. 125 kHz in the present case of 30 mm radius and 10 mm height). The effects of specimen shape and electrode locations are tested. Various Quartz grain alignment schemes are tested and even the worst case of having a 50%:50% mixture of right- and left-handed Quartz crystals without any preferred orientation show stresses of about 1 MPa at the resonance frequency. The simulation results suggest that HF-HV-AC piezoelectric excitation of Quartz bearing rocks could be a potential pre-treatment technique in comminution.

Effects of specimen shape and size on the permeability and mechanical properties of porous concrete

Porous concrete, which is generally considered as an environment-friendly pavement, plays an important role in sponge city. However, measuring its strength and permeability with different specimen shapes and sizes has not been paid enough attention by the researchers. Therefore, the effects of the size and shape on the permeability and mechanical properties of porous concrete were investigated in this paper. Thus, two types of aggregates and three types of cement were selected to cast different mixtures in different molds (two sizes of cylindrical and cuboid specimens). All porous concrete specimens were tested to evaluate the influence of shape and size on the permeability of porous concrete firstly. Then the different cube and cuboid specimens were nominated to measure the compressive strength and flexural strength of porous concrete respectively. Two different sizes of cylindrical specimens were selected to test the compressive strength and splitting strength. The results show that porosity, aggregate size, aggregate type, cement grade could affect the strength of porous concrete. Moreover, the compressive strength, flexural strength, splitting strength of the porous concrete with two different sizes, and the compressive strength and splitting strength with different shapes are significantly different.

Experimental Study on the Influence of Specimen Shape on Rockburst Proneness of Red Sandstone

To investigate the specimen shape effect on rockburst proneness of rock materials, a string of conventional and single-cycle loading-unloading uniaxial compression tests was performed with cylindrical and cuboid red sandstone specimens. Despite similar development paths on stress-strain curves for the specimens with two shapes, the cuboid specimens generally show a higher uniaxial compressive strength than the cylindrical specimens. The energy evolution laws inside the two shaped specimens were explored. The results show that the input energy density (IED), elastic energy density (EED), and dissipated energy density (DED) of the two shaped specimens increased in a quadratic relationship with the increment of unloading level. Moreover, the linear relationships between the EED, DED, and IED were further confirmed for two shaped specimens, which were defined as the linear energy storage and dissipation laws, respectively. The energy storage coefficients and energy dissipation coefficients (the slopes of the linear relationships between the EED, DED, and IED, respectively) are almost independent of the specimen shape. According to the linear energy storage and dissipation laws, the peak EED and peak DED of every specimen can be calculated accurately. Finally, combining the failure process of rock specimens recorded by a high-speed camera, the elastic energy index (WET), the residual elastic energy index (AEF), and the far-field ejection mass ratio (MF) of each specimen were adopted to assess the rockburst proneness of the red sandstone sampled in cylindrical and cuboid. The results show that cuboid specimens exhibited stronger rockburst proneness than cylindrical ones, which favorably agreed with the actual failure phenomena.

Residual stress distributions in thick specimens excavated from a large circular wire+arc additive manufacturing mockup

A flat specimen and a curved specimen with a thickness of 50 mm were excavated from a large circular wire+arc additive manufacturing (WAAM) mockup. The biaxial internal residual stress distributions in the specimens were measured using the two-cut contour method. The stress distributions in the large circular WAAM mockup were deduced, and the effects of specimen shape and dimension on the remnant stress distributions in the specimens were discussed. The investigated results show that the stress in the circular WAAM mockup has a similar distribution as that in thick multipass joints at the weld centerline, the stress in the curved specimen extracted from a large circular WAAM mockup can reflect the stress distribution trend in the mockup. For specimens excavated from a large circular mockup, the specimen shape has no significant effect on the through-thickness axial stress distribution, while it has a significant effect on the hoop stress distribution.

Effects of specimen shape and process parameters on the mechanical properties of thin beryllium foils

In this work, the effects of specimen shape and process parameters on the mechanical properties of beryllium foils were investigated. Two types of foil specimens with different shapes, including rectangular and dog bone shaped specimens, and their effect on the mechanical properties of the thin beryllium foils were examined. The specimen shape was found to affect the mechanical properties of the foils. In addition, a series of experiments were carried out to examine the effect of process parameters on the mechanical properties of the foils. The effect of changes in process parameters such as the cold rolling and high-vacuum annealing was investigated.

Effect of specimen shape, silica fume, and curing age on durability properties of self-compacting concrete incorporating coarse recycled concrete aggregates

The usage of recycled concrete aggregates (RCAs) can be effected as a replacement of natural aggregates in the assurance of the environment. Utilizing these products of construction and demolition wastes in self-compacting concrete (SCC) has positive advantages such as reducing the extravagant consumption of natural supplies and decreasing carbon dioxide emissions. However, using RCAs may be affected on the properties of concrete such as reduction in compressive strength, electrical resistivity (ER), increasing in water absorption (WA) and porosity. In this study, the durability performance of SCCs containing coarse RCAs as a partial or total replacement of natural aggregates, and silica fume (SF) as a partial replacement of cement is investigated. The replacement level of SF was considered 8% by weight of cement. Replacement level of RCAs with natural aggregates is selected at 0, 25%, 50%, 75% and 100%. Fresh properties of SCC were evaluated by measuring slump flow and J-ring tests. Durability performance of hardened concrete was investigated using WA, ER and rapid chloride penetration tests. Cube and cylindrical specimens were used to recognize the effect of shape and size specimen on ER and ultrasonic pulse velocity (UPV). Results showed that replacing RCAs decreased durability performance, but using SF in mixes significantly enhanced the ER and chloride ion penetration resistance of SCC. Results illustrated that cylindrical specimens have more consistent results than cube ones. Likewise, assessing durability performance at 91 days concluded reliable results than that in 28 days.

Comparative experimental study of the mechanical and fracture properties of Portland limestone and Corsehill sandstone

An experimental investigation of the mechanical and fracture characteristics of Portland limestone and Corsehill sandstone is undertaken, aiming at enhancing understanding of the structural behaviour of these natural building stones commonly used in both new and restoration projects in Edinburgh, Scotland. A series of three-point bending and four-point bending tests on appropriately cut prismatic samples, in the presence of U-shape notches, were performed and results were interpreted following the concepts of crack mouth opening displacement and fracture energy. The critical crack opening displacement could be further investigated as a fracture criterion, in­dependently of the method used for its determination. At a second stage, the effect of specimen shape and size on flexural strength, deflection at mid-span, crack mouth opening displacement and fracture energy was studied for Port­land limestone. Despite the scattering of results, trends observed comprise (a) the negative correlation between the flexural strength of Portland limestone and the specimen span length and (b) the positive correlation between fracture energy and specimen size. Conclusions drawn are in good agreement with similar ones for other quasi-brittle materials and contribute to the assessment of the fracture behaviour of full size structural members that are often beyond the range of possible failure testing.

Strength Conversion Factors for Concrete Based On Specimen Geometry, Aggregate Size and Direction of Loading

The main goal of this study is to find out the effect of effect of specimen shape and size, aggregate size and directions of loading and placement on the compressive strength of M20, M40, M60 and M80 grades of concrete. During the experimental study, different shaped and sized concrete specimens of different concrete mix designs were tested for compressive strength at 28 days. For casting the concrete samples, totally four different moulds were utilized, which were two different sizes of cubes and two different sizes of cylinders. The cubic moulds were 100 and 150 mm. The cylindrical moulds were 150×300 and 100×200 mm. So the relationship between size and shape effect on compressive strength of concrete samples is evaluated. Casted cubes and cylinders are tested for the compressive strength under axial compression on completion of 28 days as per IS: 516-1999.In this study, the effect of specimen sizes, specimen shapes, and placement directions on concrete compressive strengths for various grades widely used is evaluated. In addition, correlations between compressive strengths with size, shape, and placement direction of the specimen are investigated. It was found that with the increase of the size of the concrete specimen, compressive strength tends to decrease. The effect of grade of concrete on the shape effectof the compressive strength decreases as the specimen size increases regardless of strength level. Conversion factors of 0.80 to 0.90 were suggested for converting compressive strength of cylinders to compressive strength of cubes. For cubes, when the placement direction is parallel to the loading direction, the compressive strength is higher than the normal case. As aggregate size increases, compressive strength is found to be increasing.

EFFECT OF SPECIMEN SHAPE ON THE COMPRESSIVE PARAMETERS OF STEEL FIBER REINFORCED CONCRETE AFTER TEMPERATURE EXPOSURE

This study investigated the effect of specimen shape (cylindrical and cubical) on the compressive strength and elastic modulus of steel fiber reinforced concrete after exposure to the temperatures of 150, 300, 450, and 600 °C. Results show that the compressive strength and elastic modulus of the composite significantly reduce with the increase in temperature, independent of the specimen shape. Additionally, a significant difference in the compressive strength and elastic modulus conversion factors for cube-cylinder was verified with the increase in temperature. This study contributes to the limited amount of studies regarding the effect of elevated temperatures on steel fiber reinforced concretes and shows that the elevated temperatures may have a significant effect in the conversion factors for cube-cylinder.

The Effect of Specimen Shape on the Mechanical Properties of Sisal Fiber-Reinforced Concrete

Introduction: Fiber reinforced concrete is becoming popular in improving the quasi-brittle failure of concrete. Natural fibers such as sisal holds great promise in this regard. It has amazing tensile strength and is renewable. This paper presents the result of an investigation carried out on the effect of sisal fiber on the compressive strength, Split tensile strength, failure mode and Poisson ratio of Sisal Fiber-Reinforced Concrete (SFRC). Methods: A mix proportion of 1:1.92:3.68 and w/c ratio of 0.47 for a target compressive strength of 35 MPa was used. Sisal fiber was added at percentages of 0.5%, 1.0%, 1.5%, and 2.0% by weight of cement. The effect of specimen shape on the compressive strength of sisal fiber-reinforced concrete (SFRC) was reported. The compressive strength of cube (150mm X 150mm) and cylinder (150mm diameter and 300mm height) specimen was determined at 7 and 28 days, while Split tensile strength and Poisson ratio were obtained using cylindrical specimen (150mm diameter and 300mm height). Results and Conclusion: The result shows that the addition of sisal fiber slightly reduces the compressive strength of concrete, increases its split tensile strength up to 47.167% of the control specimen, arrests crack propagation and reduces its Poisson ratio. The correlation between the compressive strength of cylindrical and cube specimen was established with a ratio ranging between 0.82 - 0.73. The difference in the compressive strength was found to increase with rise in the percentages of sisal fiber. Based on the ratio and mechanical properties, 1.0% sisal fiber content was recommended as the optimum for reinforcing concrete.

Torsion Strength Measurement of Engineering Ceramics

This paper discusses the relationship between torsion strength and bending strength of Al2O3 and Si3N4 ceramics. Measurement of the torsion strength was carried out by a simplified torsion test method proposed by Yasuda and Tsutsumi. In this experiment, the average torsion strength was approximately 2/3 of its average bending strength for both ceramics. By estimating the characteristic strength σ0 in Weibull distribution from the strength data, σ0 in torsion is almost the same as that in bending, which agrees to the basic discussion in mechanics of materials. The characteristic strength σ0 is one of the normalized strength by eliminating the effects of specimen shape, dimensions and also its stress distribution, and therefore the apparent difference between torsion and bending strengths can be explained by the difference in effective surface area (Conversely, the measured torsion strength data by the simplified method must be reasonable). It reveals that biaxial fracture in tension/compression during torsion test is equivalent to uniaxial tensile fracture by this experiment.

Investigating the fracture behavior of Portland limestone: an experimental study

An experimental investigation of the mechanical and fracture characteristics of the ‘Grove Whitbed’ Portland limestone is undertaken aiming to enhance understanding of the structural behavior of this natural building stone, commonly used in both new and restoration projects in Edinburgh, Scotland. A series of prismatic specimens, bearing a machined notch at their mid-span and comprising combinations of three different geometries (span/depth ratios) and three different sizes (span lengths) were subjected to three-point bending testing. The effect of specimen shape and size on flexural strength, deflection at mid-span, crack mouth opening displacement (CMOD) and fracture energy was studied. Despite the scattering of results which is significant but common in studies of the mechanical behavior of similar geomaterials, trends observed comprise (a) the negative correlation between the flexural strength of Portland limestone test specimens and their span lengths for all three shapes and (b) the positive correlation between fracture energy and specimen size. Conclusions drawn are in good agreement with similar ones for other quasibrittle materials and contribute to the assessment of the fracture behavior of full size structural members that are often beyond the range of possible failure testing.

Effective response of classical, auxetic and chiral magnetoelastic materials by use of a new variational principle

This work provides a rigorous analysis of the effective response, i.e., average magnetization and magnetostriction, of magnetoelastic composites that are subjected to overall magnetic and mechanical loads. It clarifies the differences between a coupled magnetomechanical analysis in which one applies a Eulerian (current) magnetic field and an electroactive one where the Lagrangian (reference) electric field is usually applied. For this, we propose an augmented vector potential variational formulation to carry out numerical periodic homogenization studies of magnetoelastic solids at finite strains and magnetic fields. We show that the developed variational principle can be used for bottom-up design of microstructures with desired magnetomechanical coupling by properly canceling out the macro-geometry and specimen shape effects. To achieve that, we properly treat the average Maxwell stresses arising from the medium surrounding the magnetoelastic representative volume element (RVE), while at the same time we impose a uniform average Eulerian and not Lagrangian magnetic field. The developed variational principle is then used to study a large number of ideal as well as more realistic two-dimensional microstructures. We study the effect of particle volume fraction, particle distribution and particle shape and orientation upon the effective magnetoelastic response at finite strains. We consider also unstructured isotropic microstructures based on random adsorption algorithms and we carry out a convergence study of the representativity of the proposed unit cells. Finally, three-phase two-dimensional auxetic microstructures are analyzed. The first consists of a periodic distribution of voids and particle chains in a polymer matrix, while the second takes advantage of particle shape and chirality to produce negative and positive swelling by proper change of the chirality and the applied magnetic field.

Short-Term Stable Crack Propagation through Polyolefin Single- and Bilayered Structures - Influence of Welding, Composition and Direction of Crack Propagation

The overall stable crack initiation and propagation behaviour of specimens cut from plastic pipes that were composed of different polyolefin materials were investigated using concepts of elastic–plastic fracture mechanics including the crack propagation kinetics. The effect of specimen shape, orientation, welding, lading rate, composition/microstructure and direction of crack propagation on the crack resistance (R) behaviour of these materials has been thereby assessed.

Forming limit in thermal cruciform biaxial tensile testing of titanium alloy

In this study, a new cruciform biaxial tensile testing technology was employed to evaluate the thermal limit strains of a TA1 titanium alloy, which is widely used as an aircraft structural component, so as to prevent fracture defects during thermoplastic processing. The effect of specimen shape on the forming limit and its measurement range is discussed. The results of this study show that a design that reduces the semispherical thickness results in localized necking and fracture at the center of the specimen when normal stress is applied to it. The forming limit diagrams obtained at different angles with respect to the material rolling direction suggested that the limit strain was anisotropic in nature. The experimental results were in good agreement with the substituted values obtained from the finite element analysis and Oyane ductile fracture criterion. Finally, the efficacy of the related test and prediction methods was corroborated.

Evaluation of AASHTO T 324 Hamburg-Wheel Track Device test

The Hamburg Wheel-Track Device (HWTD) test has recently gained popularity among many state highway departments of transportation (DOTs) for use in hot mix asphalt (HMA) moisture sensitivity evaluation. In this paper, suggestions are presented to improve and provide more consistent and representative results for this test as described in AASHTOT324 – Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA). In the AASHTOT324 specification, either a cylindrical or a slab specimen can be tested. Use of a two-dimensional micromechanics finite element (2D-MMFE) analysis has demonstrated significant gap/bonding and specimen shape effects on HWTD test results for the cylindrical specimen setup. In addition, the analysis suggests the best method for defining the “rut depth” to ensure consistent results between two specimen setups. Results of this study have concluded that: (1) slab specimens can provide more reliable test results due to larger size and uniform geometry; (2) two cylindrical specimens (cores) should be glued together to prevent localized failure due to larger peak maximum principal strains when there is no bonding; (3) measurements of average rut depth should be collected from stations near the centers of cylindrical specimens to keep the specimen shape effects to the lowest possible level; and, (4) an agency should not allow both specimen setups to be used interchangeably in the HWTD specifications. The investigation also suggests that the average rut depth evolution curve fitted using a three-stage Weibull approach can define the number of passes to failure and define the stripping initiation point (SIP) better than the visually determined SIP.

Effect of length-to-diameter ratio on the unconfined compressive strength of cohesive soil specimens

In this work, the influence of the length-to-diameter ratio (L/D) on the unconfined compressive strength (UCS) of cohesive soil specimens was assessed. An L/D ratio of between 2 and 3 is generally recommended by accepted scientific and technical authorities. Nevertheless, published reports on the effect of specimen shape on soil strength are scarce. Therefore, we determined the effect of specimen shape on the UCS values of four clay soils by testing compacted cylindrical specimens with L/D ratios ranging from 0.5 to 3. The test results indicated that the UCS value decreases significantly with increasing L/D ratio. This decrease becomes particularly steep when the L/D ratio exceeds 1, but then becomes less steep when the L/D ratio is between 1.25 and 2.5. In addition, the failure pattern generally changes from ductile to brittle and the failure mechanism develops in quite complex and obscure ways when the L/D ratio is ≥2.75. Based on an analysis of the results, correction formulae with strong statistical relationships were determined for the soils tested in this study. Nonetheless, further investigation is needed to check the validity of the equations derived for these soils.

The effect of specimen shape and strain rate on uniaxial compressive behavior of rock material

The mechanical properties of rock material with length/diameter ratios varying from 1.0 to 3.0 were determined using a newly developed servo-hydraulic machine at a wide range of strain rates. The uniaxial compressive strength, initiation and dilatancy stresses, peak axial strain, and strain energy gradually decreased with increasing length/diameter ratios at the same loading condition; for the same length/diameter ratio, these properties increased with increasing strain rate. The elastic modulus increased with increasing specimen shape and strain rate, whereas the Poisson’s ratio was independent on these two factors. The fracture modes were significantly dependent on both strain rate and specimen shape. When the strain rate was below 10−3 s−1, splitting was the main fracture mode for the short specimens while the shearing fracture mode dominates the longer specimens; when the strain rate was above 10−3 s−1, the fracture mode changed directly from cone-shaped fractures to shearing fractures. The recommended length/diameter ratio was 2.5 at strain rates of 10−5–10−2 s−1.

807 CFRP積層板の非線形挙動に及ぼす試験片形状と端部拘束の影響の有限要素解析(OS8-(2),OS8 オーガナイズドセッション≪複合材料の変形と破壊およびマルチスケール計算技術≫)

807 CFRP積層板の非線形挙動に及ぼす試験片形状と端部拘束の影響の有限要素解析(OS8-(2),OS8 オーガナイズドセッション≪複合材料の変形と破壊およびマルチスケール計算技術≫)