The possibility of using the dynamic shear rheometer (DSR) with 4 mm parallel plates and 3 mm gap is investigated as an alternative experimental method to measure the rheological properties of ...asphalt binders at low temperature. A special butterfly silicone mold was prepared for this purpose and the corresponding testing procedure was also developed. Five different asphalt binders, which are part of two active research projects, were selected. Frequency and temperature sweep tests were conducted using the DSR with three plate–plate geometries: 4 mm, 8 mm, and 25 mm. The new testing procedure was used to measure at low temperatures. The method recently proposed by the Western Research Institute and based on DSR tests with 4 mm parallel plates and 1.75 mm gap was also used for comparison purposes. Black diagrams and Cole-Cole plots were then used to evaluate the experimental data. Complex modulus and phase angle master curves were generated, and the rheological parameters compared. Finally, the two spring, two parabolic elements, one dashpot (2S2P1D) model was selected to investigate the rheological properties of the binders. Results indicate that the proposed procedure is a simple and reliable experimental method and represents an alternative experimental option to measure and analyze the rheological properties of asphalt binders at low temperature.
The development of products in a variety of industries is now being increasingly influenced by material advancements. Many experts are looking for basic materials that are strong, light, and ...inexpensive. Solids are often rather thick, whereas light materials are weaker. To attain significant strength while lowering weight, we use composite materials. This work deals with the mixed effects of composites made by hand using an epoxy tar and a hardener along with different fiberes of chopped mate (KC), Kenaf (KA), and Kevlar (KB). Mechanical studies such as tensile (UTS), flexural (FL), impact (IM), and hardness (BHN) were conducted after creating specimens according to standard measurements.
This paper focuses on modelling inelasticity of additively manufactured polylactide (PLA) thermoplastic using Fused Deposition Modelling (FDM) printing technology. The material response of PLA is ...viscoplastic and temperature-dependent, as is typically seen for thermoplastics. The inelastic deformation of printed PLA undergoes initial yielding, strain softening, and subsequent failure. The Three-Network (TN) constitutive model was employed in this work, which captures experimentally observed material response and consists of three molecular equilibrium and time-dependent viscous networks that act in parallel. The parameter identification was performed in accordance with experimental data from uniaxial testing and a validation experiment was carried out by loading plate with a hole and measuring its strain distribution using Digital Image Correlation (DIC) method, which was compared with the predictions from Finite Element Analysis (FEA).
Material developments are now playing an progressively important role in the development of produces in a variation of industries. Many experts are seeking for fundamental materials with high ...strength, low weight, and low cost. Solid solids are typically somewhat thick, while light materials have lower strength. We use composite materials to achieve great strength while reducing weight. This task deals with the mixed effect of composites constructed of Kenaf (KE), Kevlar fibres (KF), as well as chopped mate (CE) that are created by hand using an Epoxy tar and a hardener. After making varieties as per regular measurements, mechanical experiments such as Tensile (TS), Flexural (FS), impact (IS) and hardness (HN) were carried.
•In vitro puncture studies have lacked consistent, appropriate boundary conditions.•Natural tension may be determined from location-specific shrinkage experimentation.•Initial tension and ...pre-conditioning significantly affect puncture force of skin.•Greater skin thicknesses correlated with greater forces at failure.•Pre-conditioning substantially reduced hysteresis and variation in skin samples.
Quantifying the mechanical behavior of skin has been foundational in applications of cosmetics, surgical techniques, forensic science, and protective clothing development. However, previous puncture studies have lacked consistent and physiological boundary conditions of skin. To determine natural skin tension, excision of in situ porcine skin resulted in significantly different diameter reduction (shrinkage) in leg (19.5 %) and abdominal skin (38.4 %) compared to flank skin (28.5 %) (p = 0.047). To examine effects of initial tension and pre-conditioning, five conditions of initial tension (as percentage of diameter increase) and pre-conditioning were tested in quasistatic puncture with a 5 mm spherical impactor using an electrohydraulic load frame and custom clamping apparatus. Samples with less than 5 % initial tension resulted in significantly greater (p = 0.011) force at failure (279.2 N) compared to samples with greater than 25 % initial tension (195.1 N). Eight pre-conditioning cycles of 15 mm displacement reduced hysteresis by 45 %. The coefficient of variance was substantially reduced for force, force normalized by cutis thickness, displacement, stiffness, and strain energy up to 46 %. Pre-conditioned samples at physiological initial tension (14–25 %) resulted in significantly greater (p = 0.03) normalized forces at failure (278.3 N/mm) compared to non-conditioned samples of the same initial tension (234.4 N/mm). Pre-conditioned samples with 14–25 % initial tension, representing physiological boundary conditions, resulted in the most appropriate failure thresholds with the least variation. For in vitro puncture studies, the magnitude of applied initial tension should be defined based on anatomical location, through a shrinkage experimentation, to match natural tension of skin. Characterizing the biological behavior and tolerances of skin may be utilized in finite element models to aid in protective clothing development and forensic science analyses.
To improve the accuracy of a sheet metal forming simulation, the constitutive model is calibrated using results from multiaxial material testing. However, multiaxial material testing is ...time-consuming and requires specialized equipment. This study proposes two different deep neural network (DNN) approaches, a two- and three-dimensional convolutional neural network (DNN-2D and DNN-3D), to efficiently estimate biaxial stress-strain curves of aluminum alloy sheets from a digital image representing the sample's crystallographic texture. DNN-2D is designed to estimate biaxial stress-strain curves from a digital image of {111} pole figure, while DNN-3D estimates the curves from a 3D image of the texture. The two DNNs were trained using synthetic texture datasets and the corresponding biaxial stress-strain curves obtained from crystal plasticity-based numerical biaxial tensile tests. The accuracy of the two trained DNNs was examined by comparing the results from that of the numerical biaxial tensile tests. It was observed that both the DNNs could estimate biaxial stress-strain curves with high accuracy. Though DNN-3D provides with a better estimation than DNN-2D, it displays lower computational efficiency. Thus, the two DNNs and their training procedures offer a new and efficient method to provide virtual data for material modeling.
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•DNNs were used to estimate biaxial stress-strain curves of aluminum alloy sheets.•Pole figure images and 3D orientation maps were explored as input data.•DNNs were as accurate as numerical biaxial tensile tests, but much faster.•A new approach to virtual data generation for material modeling was demonstrated.
•Study investigates transverse material property gradient through bamboo culm wall.•Transverse behaviour does not behave as a fibre-reinforced composite material.•Variation if morphology through culm ...wall identified using microscopy.•Culm wall morphology coupled with material property assessment.
Performance of full-culm bamboo structures is dominated by longitudinal splitting behaviour, often exacerbated by connection details. This behaviour is a function of the transverse properties of this highly orthotropic material. Considerable study of the longitudinal properties of bamboo is available in which it is often concluded that bamboo may be considered as a fibre-reinforced composite material and material properties may be assessed using rule-of-mixture methods. Nonetheless, few studies have addressed the transverse properties of the bamboo culm wall, despite these largely governing full-culm behaviour. This study investigated the transverse material property gradient through the culm wall and attempts to connect the mechanical results to physical observations and phenomena. Most importantly, the study demonstrates that the complex transverse behaviour of bamboo does not appear to behave as a classic fibre-reinforced composite material in the direction transverse to the fibres. In this study, five different bamboo species, Phyllostachys edulis, Phyllostachys bambusoides, Phyllostachys meyeri, Phyllostachys nigra, and Bambusa stenostachya were tested using a modification of the flat-ring flexure test to obtain a measure of the transverse tensile capacity of the bamboo. Microscopy analyses are used to qualitatively describe the culm wall architecture and to quantitatively assess the failure modes through the culm wall thickness.
The in-plane torsion test offers an alternative to common parameter identification tests needed for material modeling of sheet metal. As compared to common tests during material characterization, ...higher equivalent plastic strains are achieved, and kinematic hardening laws are calibrated at higher strains. In addition it also allows the determination of fracture strains in pure shear. In this contribution, we focus on a well known approach utilizing optical measurement of a scribed line as indicator for the shear deformation. The underlying mathematical model is studied, and an error analysis is provided regarding the approximation of stress and strain measures. Thereby, the assumption of simple shear deformation is found to be accurate for specimens of the assumed geometrical and material properties. The presented approach, however, can be easily adapted to derive error estimates also in cases of differing geometry or material.
•The in-plane torsion test is an alternative to common material tests for sheet metal.•A multitude of assumptions are typically made for stress and strain calculation.•Yield curves and error estimates due to these assumptions are presented.•Recommendations regarding the quality of various simplified solutions are given.
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