Response Characteristics Of Materials Research Articles

Combined effect mechanism of linear loading and disturbance with different amplitudes on sandstone

To comprehend the stress state and response characteristics of materials under complex conditions, researchers have decomposed stress states into fundamental paths and investigated diverse path combinations. To ensure comparability, four identical samples were carefully selected from a pool of 100 samples using ultrasonic tests based on the wave speed and waveform characteristics. These samples underwent specially designed stress paths to analyze the combined effects of linear loading and perturbation. Our result analysis centred on the perturbation amplitude and stress levels during composite action, revealing intricate relationships between the stress levels, strain, and nonlinear/linear energy evolution under complex stress paths. Simultaneously, 3D surface fractures were precisely reconstructed using the YOLOv5 and FAST feature point detection algorithms, elucidating the evolving patterns of the fractures. As a result of our study, the rotation trend of the main fracture was validated by integrating mechanics and P-wave reflection rules. Notably, our experimental results closely aligned with the theoretical predictions, showing the reliability of our study. These findings can significantly contribute to guiding safety protocols in the field of underground engineering.

Effects of iron impurities on the photoelectric response characteristics of silicon.

Since Fe contamination is easily mixed into Si-based photoelectric materials during the fabrication process, the relative changes of energy levels and photoelectric properties of Si material mixed with Fe impurities in different occupancy sites are studied. Based on the first principle and photoelectric response theory, an analysis model of the response characteristics of Si material mixed with Fe impurities is established. The changes of the material's electronic structure are calculated, and the effects of different occupancy sites of Fe impurities on the photoelectric response characteristics of materials are comparatively analyzed. Results show that when the Fe atom occupies the tetrahedral interstitial site in Si, the energy band structure and response characteristics of the material are relatively obviously affected. In this case, the impurity energy band introduced by the Fe impurity passes through the Fermi level, leading to the disappearance of the band gap. The absorption of Si material outside the response band is significantly enhanced. And a new absorption peak is generated at about 1530nm, with an absorption coefficient of about 25513 cm-1. Thus, the Si material can produce a relatively strong response to the light beam outside the response band. In the meantime, the saturation threshold of the Si-based photoreceptor is significantly lower than that of the other two position types. For the irradiation light at the wavelength of 1319nm, the saturation power is only 0.0035 W∙cm-2. The analysis results provide a reference for the application and development of photoelectric devices.

Control of differential-drive mobile robots for soft object deformation

The aim of this work is a control scheme implementation to deform a nonrigid object in which deformation dynamics are modeled by the finite element method. The deformation of a soft object is highly difficult to model because of its non-linearity, time-dependency, and material-response characteristics. Thus, the control implementation for Differential Drive Mobile Robots (DDMR) to deform an elastic object, is a challenge. The proposed steps to solve it are: Position-control designed over DDMR kinematics. Alignment-control applied for DDMRs orientation. The desired shape of the object is achieved using two contact points as the control nodes. A centralized vision algorithm was employed in each stage to obtain positions. To show the usefulness of the proposed scheme, numerical simulation, and real-time implementation were carried out.

The fatigue fracture characteristics of the bond zone of aluminum matrix composites (Al-12Si/ABOw) with Al-12Si alloys

The strain controlled low-cycle fatigue (LCF) test of the bond zone of aluminum matrix composites (Al-12Si/ABOw) with Al-12Si alloys was carried out with the test temperature range from 25 °C to 350 °C. The cyclic mechanical response characteristics of material at different test temperatures were analyzed. The microstructural evolution process and fracture mechanism of three characteristic fracture models were studied through SEM observation. The influence of temperatures and load magnitudes on fatigue behaviors were also discussed. The results showed that, the cyclic stress responses of the material exhibited cyclic hardening under low-cycle fatigue loading at 25 °C, and the crack occurred at the casting defects in the composite part first, resulting in a flat fracture surface with both composite part and Al-12Si alloy part. When the temperature raised to 200 °C, the cyclic stress response of the material would show out slight cyclic hardening at beginning stage and distinct cyclic softening during later stage. The casting defects in the composite would no longer be the prior crack source, and the crack would initiate at the large-sized primary Si particles nearby the bond zone which led to a fracture surface with the bond zone shape under low-cycle fatigue loading at 200 °C. With the continued increasing of temperature to 350 °C, the cyclic stress responses of the material showed the characteristics of continuous softening, and the fatigue crack generated at the primary Si phases in the Al-12Si alloy part, which caused the specimens fractured at the unreinforced Al-12Si alloy parts with a fracture surface like common aluminum alloy fracture under high temperature. There was one point had to be mentioned that when the magnitude of cyclic strain loadings (△ε/2) was larger than 0.003, the failure mode would be the fracture of the unreinforced Ai-12Si alloy part at any temperature due to the prior fracture of Al-12Si matrix alloy under relatively high loadings. Microstructure observation indicated that the fatigue fracture features of the material transformed from hard-brittle to soft-ductile gradually with the change of test temperatures from 25 °C to 350 °C.

Improvement of Hardening Stiffness Test as an Indicator of Environmental Stress Cracking Resistance of Polyethylene

Long term mechanical behavior of polyethylene (PE) is of great importance especially in cases where structural integrity is required. In order to predict characteristics of the mechanical behavior of PE, it is necessary to fully understand the molecular structure of the employed resins. In this study, evaluation of several micromolecular properties of PE is conducted. These properties influence an important performance indicator of PE for structural applications, namely, the environmental stress cracking resistance (ESCR). ESCR in PE resins occurs through a slow crack growth mechanism under low applied stresses and long periods of time. This property is usually assessed by unreliable and time consuming testing methods such as the notch constant load test (NCLT) on notched PE specimens in the presence of an aggressive fluid at elevated temperatures. In the work presented herein, relationships between molecular structure and material response characteristics, mainly between molecular weight properties and short chain branching content in relation to strain hardening behavior of PE resins, were investigated based on results from tensile experiments. Inter-lamellar entanglements are believed to be the main feature controlling slow crack growth of PE. Extent of entanglements and entanglement efficiency has been investigated by monitoring the strain hardening behavior of PE resins in solid state through a uniaxial tensile test. The hardening stiffness (HS) test for prediction of ESCR was refined and improved to cover a broader range of PE resins, along with easier sample preparation, and faster testing. The improved test offers a more reliable and consistent ESCR picture without the drawbacks of the subjective notching process and ad-hoc presence of aggressive fluids.

General Basis Functions for Parametric Representation of Energy Deposition Processes

General basis functions for parametric representation of energy deposition processes are constructed according to the general physical characteristics of energy deposition within a volume of material from a beam energy source. These basis functions include previously constructed source functions as special cases. The construction of a general parameterization of energy deposition processes, e.g., welding and rapid prototyping, is necessary for inverse analysis of such processes. The structure of such a parameterization follows from the concepts of model and data spaces that imply the existence of an optimal parametric representation for a given class of inverse problems. Accordingly, the optimal parametric representation lying within the model space is determined by the characteristics of the available data, i.e., data space, which contain both experimental measurements and numerical simulation data. Experimental measurements include solidification cross-sections, thermocouple measurements, and microstructural changes. Numerical simulation data include general temperature field trend characteristics, response characteristics of materials to volumetric energy deposition, and the relative sensitivity of temperature field characteristics to phenomena occurring on different space and time scales. A general procedure is described for using basis functions with the available experimental and numerical data to construct a multidimensional field representation of a large class of energy deposition processes.

High-Quality Micromachining of Silicon at 1064 nm Using a High-Brightness MOPA-Based 20-W Yb Fiber Laser

The advances in design, performance, cost reduction, and brightness for the modern Yb fiber lasers have opened up the possibility of redefining the processing options of semiconductor materials at a wavelength of 1064 nm. The usual laser of choice for Si processing is the 355- or 266-nm diode-pumped solid-state system. The provision of a new master oscillator power amplifier (MOPA)-based high-brightness Yb-based fiber laser configuration has provided a range of pulse parameters (30-50 ns full-width at half-maximum), peak powers approaching ~2 GWmiddotcm-2, and pulse repetition rates up to 500 kHz. These processing parameters offer a broad range of material response characteristics. This paper provides a preliminary analysis of the response of Si to the new MOPA-based Yb laser operating at maximum average power of 20 W. Results presented here show no signs of the usual thermally induced deleterious effects (microcracking, heavy recast layers, and surface damage) normally associated with Si interactions at 1064 nm. Volumetric etch rates of up to 230 000 000 mum3middots-1 were observed with a high-quality percussion drilling interaction at a repetition rate of 25 kHz and an average power of 20 W.

Non-traditional machining using pulsed water jets

This paper discusses water jet machining of selected materials using a non-traditional way of delivering water jets in the form of a series of discrete pulses. The theory of water jet impact has been used to demonstrate the principle of removing material by exploiting the existence of a Rayleigh wave that excites the formation of surface cracks and the lateral outflow of water that extends the cracks and removes material. A mathematical model has been developed that predicts changes in the response characteristics of materials owing to an idealised representation of a finite jet of water impacting a plane surface. The analytical approach used is applicable to the first stages of impact where the compressibility of water in the droplet is significant. The predicted response characteristics are compared with experimental data generated using controlled water jet impacts produced by a specially constructed pulsed water jet machining centre. The predicted response of selected materials compare well with experimental data. The results presented in this paper illustrate the importance of using pulsed water jets as a way of machining materials in a non-traditional manner.

The elastoplastic response of poly(methyl methacrylate) to indentation

This paper describes an experimental and analytical study of the contact compliance and hardness of a glassy polymer, poly (methyl methacrylate), which has an elastoplastic response to indentation using rigid conical and spherical indenters. The experimental method and the associated intrinsic errors are described. The nature and importance of these errors are reviewed and a variety of corrections are applied. The potential errors addressed include the zero error, the indenter tip defect correction and the problems associated with various extrapolations and interpolations of the experimental data necessary in order to abstract the material characteristics of the polymer. The analytical description of the data has been facilitated by an adaptation of the Box-Cox transformation (Box, G. E. P. Sz Cox, D. R. 1964 J. R. Statist. Soc. 26, 211), which is shown to be a most effective way of abstracting the required material characteristics data and minimizing the influence of the intrinsic errors inherent in the compliance method. The deduced material response characteristics of the polymer, in particular the Young’s modulus and the yield stress, are shown to be consistent with data obtained by conventional mechanical testing methods.

Dipole relaxation rates of mass-loaded spherical inclusions in elastic matrix materials

It is necessary to be aware of the rise times of dominant resonances when tone bursts or wide bandwidth pulses are used to test the acoustic response characteristics of materials containing resonant inclusions. In practice the monopole of a void and the dipole of a mass-loaded inclusion are the most important basic resonances. The dipole center of mass relaxation rate of a mass-loaded, rigid spherical inclusions in an elastic matrix material is analyzed. Inclusion to matrix mass density ratios ranging from one to eight and matrix shear stiffnesses ranging over more than an order of magnitude are considered. It is found that the rise time of center of mass oscillations is much longer than that of cavity oscillations in the case of heavily mass-loaded inclusions in rigid matrix materials. In soft materials, the reverse is true. In terms of the period of oscillation at resonance, the relaxation time of the rigid dipole is less than half a period long. This rate may be viewed as the lower bound on the relaxation rates of mass-loaded viscoelastic inclusions.

Assessing the corrosion risk of plastics in fires

Corrosion risk is discussed as a component element of total fire risk, and the importance of the combustibility characteristics of materials in this connection is highlighted. The author discusses the contributions to corrosion hazard made by the ignitability of materials as well as their flame spread rates, rates of heat release and the chemical composition of their combustion products. The author illustrates this with experimental results from a programme of research into the flame and heat response characteristics of a series of filled and unfilled polymers, both halogenated and non-halogenated. The position of the Association of Plastics Manufacturers in Europe (APME) on the question of discriminatory standards is reviewed and, in this connection, the relative benefits and disadvantages of halogenated and non-halogenated materials are compared. The author draws attention to the limitations of small-scale tests in assessing the heat and flame response characteristics of materials (often referred to as ‘fire properties’). The need for qualification procedures of relevance to end-use performance is emphasised.

KINETORHEOLOGY

Annals of the New York Academy of SciencesVolume 404, Issue 1 p. 159-169 KINETORHEOLOGY Viscoelastic Response Characteristics of Materials Undergoing Chemical Change A. Silberberg, A. Silberberg Department of Polymer Research Weizmann Institute of Science Rehovot, Israel 76100Search for more papers by this authorM. Hennenberg, M. Hennenberg Department of Polymer Research Weizmann Institute of Science Rehovot, Israel 76100Search for more papers by this author A. Silberberg, A. Silberberg Department of Polymer Research Weizmann Institute of Science Rehovot, Israel 76100Search for more papers by this authorM. Hennenberg, M. Hennenberg Department of Polymer Research Weizmann Institute of Science Rehovot, Israel 76100Search for more papers by this author First published: May 1983 https://doi.org/10.1111/j.1749-6632.1983.tb19450.xCitations: 1AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume404, Issue1Fourth International Conference on Physicochemical HydrodynamicsMay 1983Pages 159-169 RelatedInformation

Significance of Response Characteristics of Materials to Dynamic Loading

Significance of Response Characteristics of Materials to Dynamic Loading

Significance of Response Characteristics of Materials to Dynamic Loading

The study of the behaviour of material under the influence of dynamic loads has been pursued, to a large extent, for practical reasons. It has been recognized for almost one hundred years that the deformation behaviour of materials will, in general, change as the rate of loading is increased. Within the realms of the mechanics of solids. this time-dependence of the stress/strain relationship has been treated as a fundamental problem; in the context of engineering practice it has been recognized as being a significant factor controlling the design and manufacture of engineering products. There are three major areas where better understanding of the material is of immediate interest. These are fracture mechanics, metal cutting and forming, and the development of engineering metals and alloys, their heat-treatment, and the production control of their quality. Of course none of the boundaries of these areas can be delineated with any degree of exactness. For example, criteria for fracture resistance are of interest in metal fatigue work, structural dynamics, plasticity, and shortduration life-cycle applications. Also, the growing importanc of plastics in engineering has stimulated the development of new methods of testing to evaluate their suitability in applications traditionally reserved for metals. Because of the high rate-sensitivity of plastics, their deformation and strength under dynamic, loading forms a central part of such evaluations. Much of what has been learned from metals testing is also of direct or indirect interest to the plastics problem.