Testing Of Engineering Materials Research Articles

PENGUJIAN KEAUSAN ALUMUNIUM MATRIX KOMPOSIT DIPERKUAT DENGAN KARBON NANOTUBE

Wear testing of engineering materials is an important aspect in evaluating their performance and durability. This study aims to investigate the wear-resistant ability of aluminum composites reinforced with carbon nanotubes (CNTs). The composite manufacturing process was carried out by infiltrating CNTs into the aluminum matrix through powder metallurgy method. Tests were conducted using two methods, namely pressing and sintering with temperature variations of 0oC (non sintering), 400oC, 500oC, 600oC and 700oC. The results showed that the specific wear value on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.003632850 mm3/kg.m and the highest value at a sintering temperature of 700oC with a value of 0.042771207 mm3/kg.m. And the wear rate on the specimen obtained the best value at a sintering temperature of 400oC with a value of 0.447887285 mm3/s and the highest value at a sintering temperature of 700oC with a value of 1.155387594 mm3/s. This shows that the addition of temperatures greater than 400oC has a major influence on the specific wear value and wear rate of sintering products. In addition, this method is also a reference for further researchers in developing aluminum carbon nanotube technology to obtain optimal results.

Impact detection method based on the ratio of mechanoluminescence intensity

This paper proposes an impact detection method based on the ratio of mechanoluminescence (ML) intensity, as an improvement over traditional methods that rely on absolute ML intensity. The study utilized two types of ML materials, ZnS:Cu2+ and ZnS:Mn2+, which were physically mixed and embedded them in polydimethylsiloxane (PDMS) to fabricate a flexible film sensor. A drop ball experimental setup was constructed, and the ML spectrum of the film sensor under the impact of a small ball was collected through a spectrometer. This established the relationship between impact velocity and the ratio of ML intensities. Experiments proved that the distance of spectral collection has a minimal effect on the measurement results of this method. Compared to traditional methods based on absolute ML intensity, this method has stronger resistance to environmental interference and better applicability. This new impact detection method based on the ratio of ML intensities has broad application prospects in future engineering applications, safety assessments, and material testing.

Impact of Electric-Arc Welding on The Mechanical Properties of AISI 1055 Medium Carbon Steel with Varied Gauge Diameters

Purpose: This paper investigated through experimentation, the impact of electric-arc welding processes on the mechanical properties of AISI 1055 steel medium carbon steel material with varied gauge diameters.
 Design/Methodology/Approach: The study used experimental and analytical methods to investigate the impact of electric arc welding on the mechanical properties of AISI 1055 Medium Carbon Steel. The test samples were prepared based on the standards of the American Iron and Steel Institute (AISI), with varied gauge diameters. Standard tensile tests were performed on the samples before welding and after welding, using a computer-interfaced Universal Tensile Testing Machine. Data obtained from the study was analyzed using graphs, tables and charts. Finally, the sets of results for both welded and unwelded specimens were compared to determine the impact that welding has on welded medium carbon steel components and structures.
 Findings: The data recorded by the computer-interfaced tensile test machine was used to plot and display, the stress-stain graphs for the various sets of samples. The results showed that the welding processes adversely affected the Ultimate Tensile Strength (UTS), Yield Strength, Elastic Modulus and Impact Strength of the samples studied; since all the samples studied had their initial values dropped after undergoing welding and testing. However, the strain of the samples increased after welding.
 Research Limitation/Implication: Although there are other methods and techniques of welding metals, this study adopted electric arc welding to weld the samples used for the study due to resource constraints.
 Practical Implication: The findings of this study also bring to the fore, the need for industry regulators to promulgate standards to regulate the welding of medium carbon steel and by extension, other industrial materials to preserve the natural properties of the materials.
 Originality/Value: This study introduced an important perspective to the testing of engineering materials by varying the gauge diameters (a key determinant of the dimensional specifications of the specimen), to obtain a comprehensive insight into the impact of electric-arc welding on the mechanical properties of the material.

AN APPROACH TO SUBPIXEL ACCURACY WIDENING CRACK WIDTH DETERMINATION IN IMAGE SEQUENCES

Abstract. As an extension to existing work on crack detection and subpixel accuracy crack width determination as a tool for civil engineering material testing, the paper shows an algorithmic approach to handle widening cracks with relative rotations between related crack borders. In the first time step under zero-load, a set of points to be tracked through consecutive frames of an image sequence is defined. Then, subpixel-precise displacement fields are computed for the image data of the following time steps using an 8-parameter least-squares matching approach. The points are triangulated into a mesh, and the changes of the inner geometry of the triangles are considered with a mathematical model assuming a split of each triangle. With this model, subpixel-precise deformation vectors are derived. Crack candidates are determined by a thresholding applied to the vectors’ lengths. After an estimation of the crack normal, a decomposition of the deformation vectors is applied, allowing to compute crack widths and shear movements. As a novel contribution to the technique, a model extension is proposed for the case of a relative rotation between the crack borders in order to reduce systematic errors. The model includes two separate rigid transformations for each crack side.

3D LEAST SQUARES MATCHING APPLIED TO MICRO-TOMOGRAPHY DATA

Abstract. The paper introduces 3D least squares matching as a technique to analyze multi-temporal micro-tomography data in civil engineering material testing. Time series of tomography voxel data sets are recorded during an in-situ tension test of a strain-hardening cement-based composite probe at consecutive load steps. 3D least squares matching is a technique to track cuboids in consecutive voxel data sets minimizing the sum of the squares of voxel value differences after a 12-parameter 3D affine transformation. For a regular grid of locations in each voxel data set of the deformed states, a subvoxel-precise 3D displacement vector field is computed. Discontinuities in these displacement vector fields indicate the occurrence of cracks in the probes during the load tests. These cracks are detected and quantitatively described by the computation of principal strains of tetrahedrons in a tetrahedral mesh, that is generated between the matching points. The subvoxel-accuracy potential of the technique allows the detection of very small cracks with a width much smaller than the actual voxel size.

Influence of Aggregates in Concrete on Fiber-Optic Based Thermal Integrity Profiling Analysis of Concrete Structures

Fiber-optic sensor has drawn wide attention in the nondestructive testing and evaluation of civil engineering materials due to its high accuracy and resolution as well as cost-efficiency. Currently, using optical fiber as the temperature sensor is proposed to conduct the thermal integrity profiling (TIP) of concrete structures. However, concrete is not a thermally homogeneous material as assumed in current studies of concrete TIP. Its essential components, such as aggregates may cause thermal inhomogeneity problems when implementing fiber-optic sensors for TIP. In this paper, we use the concrete structures with different grades of aggregates to conduct numerical simulation for nondestructive thermal testing. The goal is to investigate how the thermal inhomogeneity caused by aggregates would influence the testing result. Firstly, we establish three concrete structure models with three different grades of aggregates based on the scenarios where these concrete structures will be used. Then, we numerically simulate the thermal process on these models and extract the temperature at the location where optical fiber would be installed. The influence caused by the inhomogeneity of aggregate size and distribution as well as the possible method to minimize the effect are evaluated in the paper. Overall, aggregates of concrete have a significant influence on the accuracy of TIP analysis, and defects could be veiled if no proper treatment to the data is implemented for TIP analysis.

Photogrammetric determination of 3D crack opening vectors from 3D displacement fields

This publication presents a procedure for the determination of all three components of crack opening vectors from stereoscopic image sequences of a specimen under load in civil engineering material testing. The method is based on analyzing stereoscopic image sequences of a concrete specimen with a surface texture, which is suitable for applying image matching techniques. Spatio-temporal correspondences are established by applying sub-pixel accuracy area based image matching techniques to a grid of surface points. Data acquisition starts at zero load. The load is stepwise or continuously increased during the experiment. The surface points are matched between the stereo images and tracked through each camera image sequence. As an intermediate result, we obtain a set of 3D object surface points for each epoch by spatial intersection. These 3D object points are triangulated into a mesh. Then, the mesh triangles are tested for deformations by transforming the triangles into 2D space and computing the norm of the 2D relative translation vector. Connected components of deformed triangles are determined and crack normals are computed. In the next step, the 3D relative translation vector can be derived for each deformed triangle. Defining local crack opening coordinate systems for the deformed triangles, the three components of the crack opening vectors can be computed. The method has been tested and validated in practical experiments. The technique is capable of quantitatively analyzing cracks with a width of less than one pixel in image space.

A new technique for tensile testing of engineering materials and composites at high strain rates.

A new test technique and bespoke apparatus to conduct high strain rate measurements of the tensile response of materials are presented. The new test method is applicable to brittle solids and composites as well as high-performance fibres, yarns and tapes used in composite construction. In this study, the dynamic response of monolithic poly(methyl methacrylate) and unidirectional composites based on Dyneema® tape, Dyneema® SK75 yarn and Kevlar® 49 yarn are explored. The technique allows early force equilibrium and yields valid tensile stress-strain curves, which include part of the elastic material response. The new method also enables investigation of size effects in tape and yarn materials, allowing testing of specimens of arbitrary length.

On the Importance of Building Engineering Materials Detection in the New Period

With the rapid development of economy and technology, there are moreand more types of construction engineering materials, and more and more inputs. In order to ensure the overall quality of construction projects, we must pay attention to the quality inspection of construction materials. Because the inspection is affected by many factors, resulting in inaccurate test results, it is necessary to continuously increase the supervision of the construction materials inspection work, improve the comprehensive quality of the inspection personnel, and thus improve the accuracy of the quality inspection of construction materials and promote the healthy and long-term development of China's construction industry. The article mainly analyzes the importance of building engineering material testing and proposes several optimization strategies for building engineering material testing technology.

Advanced spatio-temporal filtering techniques for photogrammetric image sequence analysis in civil engineering material testing

The paper shows advanced spatial, temporal and spatio-temporal filtering techniques which may be used to reduce noise effects in photogrammetric image sequence analysis tasks and tools. As a practical example, the techniques are validated in a photogrammetric spatio-temporal crack detection and analysis tool applied in load tests in civil engineering material testing. The load test technique is based on monocular image sequences of a test object under varying load conditions. The first image of a sequence is defined as a reference image under zero load, wherein interest points are determined and connected in a triangular irregular network structure. For each epoch, these triangles are compared to the reference image triangles to search for deformations. The result of the feature point tracking and triangle comparison process is a spatio-temporally resolved strain value field, wherein cracks can be detected, located and measured via local discrepancies. The strains can be visualized as a color-coded map. In order to improve the measuring system and to reduce noise, the strain values of each triangle must be treated in a filtering process. The paper shows the results of various filter techniques in the spatial and in the temporal domain as well as spatio-temporal filtering techniques applied to these data. The best results were obtained by a bilateral filter in the spatial domain and by a spatio-temporal EOF (empirical orthogonal function) filtering technique.

Material data matter — Standard data format for engineering materials

Standardisation is often linked to the very existence of an industry and its evolutionary dynamics especially in sectors where activities are particularly reliant on network economies. This paper investigates the interests of the stakeholders of the materials industry in the effort of setting the basis for standard-compliant formats for engineering materials test data used in materials test certificates (TCs). Test certificates provide a guarantee of origin, characteristics and materials specifications. A transition to standardised electronic-test certificates (E-TCs) is thought to offer advantages over the static alternatives currently in use. This work highlights that the stakeholders involved in the process have a general need for a standard compliant data model yet their particular interests might not be completely aligned. The choice of an open, non-proprietary, data format and compatibility of the standard with legacy technological solutions prove to be critical for the implementation of standardised E-TCs.

Gas-Adsorption Indicator Method for NDT and Surface-Defect Characterization

The gas-adsorption indicator method (GAIM) is a relatively unknown yet reliable technique for nondestructive testing (NDT) of engineering materials, and component parts. Invented in Russia, GAIM is a spin-off from the BURAN space program in the former Soviet Union. GAIM is inspired on a highly effective method to detect defects on the tiles of the thermal protection system (TPS) of BURAN and leakages through seals in compartment hatches of the spacecraft. This method involved the capture of gas molecules by a chemically treated sheet. Based on this technique, GAIM was derived and developed into an innovative penetrant technique (PT) for NDT and NDE of surfaces. GAIM offers clear advantages over more conventional PT methods and other techniques for surface NDT and NDE. GAIM proves to be more versatile, adaptable, considerably less expensive, safer, and more reliable. It allows fast inspections, detections, and characterization of surface anomalies, such as cracks, corrosion, and micro-porosity. The technique can be used in a wide variety of materials, including metals, ceramics, specialized coatings, and composites. The applicability of GAIM for NDE and NDT is ample, ranging from simple lab tests to field inspections of spacecraft, aircraft, and nuclear and conventional power plants. The underlying physical phenomena and researched theory behind the technique are presented and explained. The technique is also illustrated with graphical documentation, and application examples.

MatDB Online - A Standards-Based System for Preserving, Managing, and Exchanging Engineering Materials Test Data

The CODATA Data Science Journal is a peer-reviewed, open access, electronic journal, publishing papers on the management, dissemination, use and reuse of research data and databases across all research domains, including science, technology, the humanities and the arts. The scope of the journal includes descriptions of data systems, their implementations and their publication, applications, infrastructures, software, legal, reproducibility and transparency issues, the availability and usability of complex datasets, and with a particular focus on the principles, policies and practices for open data.All data is in scope, whether born digital or converted from other sources.

Small-angle study of fuel particle coatings

Pores in a graphite coating of fuel particles were studied by small-angle neutron scattering. Small-angle scattering curves for individual coated fuel particles (CFPs) and a set of CFPs were measured. Their processing detected pores in CFP coatings. Their characteristic sizes and the specific pore volume were determined. The applicability of this technique for studying and nondestructive testing of atomic engineering materials was shown.

Cascaded image analysis for dynamic crack detection in material testing

Concrete probes in civil engineering material testing often show fissures or hairline-cracks. These cracks develop dynamically. Starting at a width of a few microns, they usually cannot be detected visually or in an image of a camera imaging the whole probe. Conventional image analysis techniques will detect fissures only if they show a width in the order of one pixel. To be able to detect and measure fissures with a width of a fraction of a pixel at an early stage of their development, a cascaded image analysis approach has been developed, implemented and tested. The basic idea of the approach is to detect discontinuities in dense surface deformation vector fields. These deformation vector fields between consecutive stereo image pairs, which are generated by cross correlation or least squares matching, show a precision in the order of 1/50 pixel. Hairline-cracks can be detected and measured by applying edge detection techniques such as a Sobel operator to the results of the image matching process. Cracks will show up as linear discontinuities in the deformation vector field and can be vectorized by edge chaining. In practical tests of the method, cracks with a width of 1/20 pixel could be detected, and their width could be determined at a precision of 1/50 pixel.

Testing environmentally assisted cracking of reactor materials using pneumatic servo-controlled fracture mechanics device

The degradation mechanism, known as stress corrosion cracking or environmentally assisted cracking (EAC) has long been recognized as a major cause of failure of components and structures but the basic mechanisms of this process are not still fully understood and the development of standardized and practicable methods of testing is a key element in a strategy to understand the kinetics of failure and to provide for mitigation measures. At the JRC-IE, Institute for Energy, a new laboratory for EAC testing of nuclear power engineering materials, in particular core internals materials, has been recently commissioned. The main part of the facility consists of a pneumatic servo-controlled fracture mechanics loading system for 3-point-bending tests of fatigue pre-cracked SEN(B) specimens of different sizes, in a high temperature and pressure autoclave. A first test campaign have been carried out and focused on comparison of the results obtained on 10×10×55 and 3×4×27 mm 3 SEN(B) 316L stainless-steel specimens loaded by constant displacement rate increase tests in typical BWR conditions. The results led to determination of the influence of the loading rate on crack initiation, comparison of the results measured on different size specimens, and verification of the usability of LEFM and EPFM parameters for evaluation of the results.

Analysis Tools Used to Evaluate Oxygen Hazards and the Oxygen Compatibility of Metals

Abstract Performing analyses of the fire hazards in oxygen systems is critical to avoiding fires. Over the years, several systematic approaches to analyzing fire hazards in oxygen systems have been proposed and analysis methodologies for oxygen systems have become more refined. Specific evaluation is performed on the compatibility of materials of construction, the presence of ignition mechanisms, and the effects that ignition or a fire would have on the component, system, and personnel. The authors of this paper routinely perform hazards analyses and failure analyses of oxygen systems for their clients and have applied new engineering technologies and materials test data to better understand, discern, and characterize oxygen fire hazards. This paper describes some of the new technologies and materials test data used and how they can be applied to evaluating the compatibility of metals in oxygen service, including three-dimensional component analysis; Computational Fluid Dynamics (CFD) flow modeling; metals flammability test data in static, flowing, and high-temperature oxygen; and metals ignition test data.

Photogrammetric Techniques in Civil Engineering Material Testing and Structure Monitoring

Civil engineering material testing includes a wide range of applications requiring the determination of the threedimensional shape of an object and changes thereof. Large structure monitoring will often include the necessity of determining object deformations at a large number of points. Photogrammetric techniques offer a large potential for the solution of a wide range of measurement tasks in this field. A modular toolbox consisting of digital cameras, computer interfaces, illumination systems, calibration devices, combined with subpixel accuracy image measurement operators, multi-image matching techniques, and self-calibrating bundle adjustment in a suitable user interface, depicts a very powerful tool for tailoring custom-made solutions for material testing labs. Due to the wide range and the repetitive nature of measurements tasks in civil engineering, these applications could depict a significant future market for photogrammetry. This paper will briefly discuss the major hardware and software modules of a toolbox for civil engineering material testing and large structure monitoring. Based on several sample applications covering object dimensions from 10 cm to 500 meters, the potential of photogrammetric deformation measurement techniques will be shown. The major advantage of photogrammetric techniques can often be seen in the fact that they allow for highly automated measurements at a large number of points simultaneously. In many cases, object deformations can be determined at a precision in the order of 1:100,000 of the object dimension, based on off-theshelf hardware components.

Techniques: science and practice

Geophysical methods can be used at and below, the ground surface, at sea, in the air, and in the laboratory. In this chapter the advantages and limitations of the main methods used in the civil engineering industry are summarised. Other, less familiar, methods are discussed with the objective of familiarising the reader with the range of possible methods, which might be suggested for the solution to a specific problem. This chapter emphasises land-based geophysical techniques to investigate the ground. There are descriptions of geophysical surveying systems, specifically developed for the marine environment to be rapid and cost-effective. Modern positioning systems, such as the Global Positioning System (GPS) and the Differential Global Positioning System (DGPS), are now in common use and accurate position-fixing of the survey vessel can be achieved. Airborne geophysical methods are widely used in regional surveys associated with hydrocarbon and mineral exploration. They currently have little application in engineering studies because their overall cost would be prohibitive in most cases. However, in a large engineering project, such as the development of a radioactive waste repository, which involves a significant requirement for regional geological information, information from large-scale seismic reflection, gravity, magnetic, and electromagnetic surveys will be required. In this case the use of airborne methods might well be both practical and economically viable. Many of the geophysical methods are widely used in the non-destructive testing (NDT) of civil engineering structures and materials. While not strictly geophysics, the testing employs the same physical parameters that control the effective use

An interactive teaching experiment in materials science

In the light of current staffing problems in Universities there is a need to examine to what extent the principles of computer aided learning can be applied objectively in small group activities where repetitive tuition is necessary. In the Engineering curricula this approach is particularly relevant to laboratory classes where much of the information to be communicated often relates to the use of complex testing equipment and where it is desirable that a full understanding of the instrumentation is obtained before testing commences. Such stringent requirements lead to the concept of an un-manned supervising computer, with which the students interact, and which can monitor learning rates and reiterate instructions if wrong responses are obtained. This paper examines current teaching psychology and concludes that there are certain vital elements in CAL. Firstly a need to recognise that students are individuals and learn at different rates, and, in particular, need to be motivated to learn. Secondly that the design of instructions should take into proper account the level of entry from previous knowledge. The laboratory experiment chosen was the uniaxial tensile testing of different engineering materials to obtain comparative data on strengths, ductility and modes of failure. A comprehensive software package was developed to run on a BBC micro-computer. The program contains all the information previously included in laboratory handouts together with question and answer routines which test understanding and control the rate of progress. Extensive use is made of graphics to represent the instrumentation in symbolic form and the computer monitors the behaviour of the apparatus and warns of improper use. Plotting of data is performed automatically. The effectiveness of the new teaching technique was examined quantitatively by obtaining critical reactions from individual students. It is concluded that student understanding and report quality is greatly improved within the original time slot for the experiment by the use of CAL techniques and that considerable savings in staff time could be obtained if such techniques were applied across the board.