Concrete Damage Identification based on Acoustic Emission and Wavelet Neural Network

In order to improve the accuracy of damage source identification in concrete based on acoustic emission testing (AE) and neural networks, and locating and repairing the damage in a practical roller compacted concrete (RCC) dam, a multilevel AE processing platform based on wavelet energy spectrum analysis, principal component analysis (PCA), and a neural network is proposed. Two data sets of 15 basic AE parameters and 23 AE parameters added on the basis of the 15 basic AE parameters were selected as the input vectors of a basic parameter neural network and a wavelet neural network, respectively. Taking the measured tensile data of an RCC prism sample as an example, the results show that compared with the basic parameter neural network, the wavelet neural network achieves a higher accuracy and faster damage source identification, with an average recognition rate of 8.2% and training speed of about 33%.

Hyperelastic models for the description and simulation of rubber subjected to large tensile loading

Purpose: Rubber is widely used in tires, mechanical parts, and user goods where elasticity is necessary. Some essential features persist unsolved, primarily if they function in excessive mechanical properties. It is required to study elastomeric Rubber's performance, which is operational in high-level dynamic pressure and high tensile strength. These elastomeric aims to increase stress breaking and preserve highly pressurised tensile strength. Design/methodology/approach: The effects of carbon black polymer matrix on the tensile feature of different Rubber have been numerically investigated in this research. Rubber's material characteristics properties were measured using three different percentages (80%, 90%and 100%) of carbon black filler parts per Hundreds Rubber (pphr). Findings: This study found that the tensile strength and elongation are strengthened as the carbon black filler proportion increases by 30%. Practical implications: This research study experimental tests for Rubber within four hyperelastic models: Ogden's Model, Mooney-Rivlin Model, Neo Hooke Model, Arruda- Boyce Model obtain the parameters for the simulation of the material response using the finite element method (FEM) for comparison purposes. These four models have been extensively used in research within Rubber. The hyperelastic models have been utilised to predict the tensile test curves—the accurate description and prediction of elastomer rubber models. For four models, elastomeric material tensile data were used in the FEA package of Abaqus. The relative percentage error was calculated when predicting fitness in selecting the appropriate model—the accurate description and prediction of elastomer rubber models. For four models, elastomeric material tensile data were used in the FEA package of Abaqus. The relative percentage error was calculated when predicting fitness in selecting the appropriate model. Numerical Ogden model results have shown that the relative fitness error was the case with large strains are from 1% to 2.04%. Originality/value: In contrast, other models estimate parameters with fitting errors from 2.3% to 49.45%. The four hyperelastic models were tensile test simulations conducted to verify the efficacy of the tensile test. The results show that experimental data for the uniaxial test hyperelastic behaviour can be regenerated effectively as experiments. Ultimately, it was found that Ogden's Model demonstrates better alignment with the test data than other models.

Statistical analysis of bamboo scrimber tensile mechanical property based on different models and experiments

PurposeBamboo scrimber is a new natural fiber-reinforced composite material in the modern industry. In this paper, the strength characteristics of this material were chosen as the object of study.Design/methodology/approachFirst, axial tensile fracture experiments were conducted on different test specimens to determine the corresponding strength data. Then three commonly used distribution models were applied to analyze the relationship between the strength and survival rate.FindingsThe results show that the tensile data demonstrate obvious dispersion. In addition, the three-parameter Weibull model fits the data best and may be used as the fundamental model for future analysis.Originality/valueSpecial statistical analysis research of the bamboo material experimental results has rarely been discovered. This paper provides a solid foundation for better understanding the mechanism of the bamboo scrimber strength phenomenon.

Mitigating Scatter in Mechanical Properties in AISI 410 Fabricated via Arc-Based Additive Manufacturing Process

Wire-based metal additive manufacturing utilizes the ability of additive manufacturing to fabricate complex geometries with high deposition rates (above 7 kg/h), thus finding applications in the fabrication of large-scale components, such as stamping dies. Traditionally, the workhorse materials for stamping dies have been martensitic steels. However, the complex thermal gyrations induced during additive manufacturing can cause the evolution of an inhomogeneous microstructure, which leads to a significant scatter in the mechanical properties, especially the toughness. Therefore, to understand these phenomena, arc-based additive AISI 410 samples were fabricated using robotic gas metal arc welding (GMAW) and were subjected to a detailed characterization campaign. The results show significant scatter in the tensile properties as well as Charpy V-notch impact toughness data, which was then correlated to the microstructural heterogeneity and delta (δ) ferrite formation. Post-processing (austenitizing and tempering) treatments were developed and an ~70% reduction in the scatter of tensile data and a four-times improvement in the toughness were obtained. The changes in mechanical properties were rationalized based on the microstructure evolution during additive manufacturing. Based on these, an outline to tailor the composition of “printable” steels for tooling with isotropic and uniform mechanical properties is presented and discussed.

Technical Basis for Flaw Acceptance Criteria for Cast Austenitic Stainless Steel Piping

According to the current ASME Code Section XI, IWB-3640 and Appendix C flaw evaluation procedure, cast austenitic stainless steel (CASS) piping with ferrite content (FC) less than 20% is treated as wrought stainless steel. For CASS piping with FC equal or greater than 20%, there was no flaw evaluation procedure in the ASME Code prior to the 2019 Edition. In this paper, the technical basis for the recently approved Code change containing flaw acceptance criteria for CASS piping is presented. The procedure utilizes the current rules in ASME Code Section XI, IWB 3640/Appendix C and the existing elastic-plastic correction factors (i.e., Z-factors) for other materials in the Code. The appropriate Z-factor to use for the CASS piping is determined based on the FC (using Hull's equivalent factor). Experimentally measured fully saturated fracture toughness and tensile data of the three most common grades of CASS material in the U.S. (CF3, CF8, and CF8M) were used to determine the flaw acceptance criteria in the Appendix C Code method. As described here, the method is conservative since it utilizes the fully saturated condition of CASS materials. In addition, it is simple and consistent with the current regulatory guidance on aging management of CASS piping.

Thermal Degradation and Mechanical Behavior of Banana Pseudo-Stem Reinforced Composites

Banana fiber has potential to be utilized in bio-based composite structures due to its low price, abundantly available and biodegradability. However, the performance of this fiber is still not comparable to the synthetic polymeric system. In this work, the thermal stability analysis and tensile test of optimized banana fiber that was initially evaluated using response surface method were conducted. The thermal analysis and the tensile test were conducted using thermogravimetric analyzer and universal testing machine respectively. It was shown that the banana fiber content offered an outstanding performance in thermal stability. The highest thermal stability however, was found in neat epoxy resin system. The TG and DTG results showed the lowest amount of residue occurred in banana/epoxy composite. The tensile data properties revealed that banana composite is comparable to synthetic samples

Mechanical Properties of Human Dura Mater in Tension – An Analysis at an Age Range of 2 to 94 Years

Realistic human head models are of great interest in traumatic brain injury research and in the forensic pathology courtroom and teaching. Due to a lack of biomechanical data, the human dura mater is underrepresented in head models. This study provides tensile data of 73 fresh human cranial dura mater samples retrieved from an area between the anterior middle and the posterior middle meningeal artery. Tissues were adapted to their native water content using the osmotic stress technique. Tensile tests were conducted under quasi-static uniaxial testing conditions with simultaneous digital image correlation. Human temporal dura mater is mechanically highly variable with regards to its elastic modulus of 70 ± 44 MPa, tensile strength of 7 ± 4 MPa, and maximum strain of 11 ± 3 percent. Mechanical properties of the dura mater did not vary significantly between side nor sex and decreased with the age of the cadaver. Both elastic modulus and tensile strength appear to have constant mechanical parameters within the first 139 hours post mortem. The mechanical properties provided by this study can help to improve computational and physical human head models. These properties under quasi-static conditions do not require adjustments for side nor sex, whereas adjustments of tensile properties accompanied with normal aging may be of interest.

Preparation and characterization of silicone rubber/graphene nanosheets nanocomposites by in-situ loading of the coupling agent

Inexpensive approach to fully disperse graphene nanosheet (GNS) in silicone rubber (SR) by the addition of (3-Aminopropyl) triethoxysilane (APTES) as the coupling agent is presented in this study. The effects of GNS loading and presence of APTES on the cure characteristics, dynamic-mechanical, rheological and mechanical properties of the resulting SR compounds were systematically studied by rheometry, DMTA and tensile testing, respectively. The obtained results were correlated with the microstructure of the samples investigated by SEM and TEM analyses. Vulcanization curves revealed that the GNS and the coupling agent had an accelerating effect on the cure kinetics of the SR compounds leading to a steady decrease in scorch time and optimum cure time along with a gradual increase in the effective torque value. Morphological results showed that the GNSs could disperse more homogeneously within SR matrix using a simple solution mixing approach by in-situ loading of APTES. DMTA results showed restricted relaxation processes in GNS-reinforced SR systems in comparison with the pure SR, with more pronounced effect for the system containing APTES owing to improved interactions between graphene and SR which prevented the molecular mobility of neighboring chains of SR matrix. The tensile data demonstrated about 20% rise of modulus in the GNS-filled rubber nanocomposites in the presence of APTES. Low-frequency rheological properties including the storage modulus (G′), the loss modulus (G″), and complex shear viscosity (η*) showed a significant increase of about 10-fold, 75% and 20%, respectively, with the incorporation of APTES and GNS. Thus it could be expected that APTES had a substantial potential to be applied in-situ as the coupling agent to fabricate SR/GNS nanocomposites with exfoliated GNS morphology and increased the rheological and mechanical properties.

Effect of Temperature and Moisture on the Tensile Properties of a TEPs-Modified Adhesive

The main factors that affect the strength of adhesive joints are the exposure to moist environments and high and/or low temperatures. The objective of this paper is to measure the water diffusion in adhesives modified with thermally expandable particles (TEPs) and assess the joint strength of water saturated modified adhesives. Bulk specimens were used to measure the diffusion coefficient of water in a TEPs-modified adhesive. The tensile data as a function of TEPs content, moisture uptake and temperature was measured. It was found that the presence of moisture and the temperature affect the mechanical properties of TEPs-modified adhesive. Further, a scanning electron microscope (SEM) analysis was performed in order to examine the fracture surfaces of the tensile specimens tested as a function of temperature and water uptake. SEM analysis showed that the absorbed moisture and temperature change the fracture mechanisms and the morphology of the specimens.