Characterization Of Mechanical Damage Research Articles

Damage characterization and microscopic mechanism of steel slag-cemented paste backfill under uniaxial compression

The utilization of steel slag-cemented iron tailings for preparing mine backfill materials can effectively consume industrial solid waste generated from steel production and significantly reduce backfilling costs. The study analyzed the influence and mechanisms of steel slag (SS) content on the mechanical damage characterization of steel slag-cemented paste backfill (SS-CPB) through uniaxial compressive strength (UCS) tests and microscopic testing methods such as X-ray diffraction (XRD) and a scanning electron microscope (SEM). The engineering applicability and economic feasibility of the material were evaluated. The main conclusions were as follows: (1) With the increase of SS content, the strength of SS-CPB first increases and then decreases, with the highest strength observed at a 10% SS content. (2) The inclusion of SS in SS-CPB leads to higher peak strain and post-peak strength, demonstrating significant plastic deformation characteristics. (3) When the SS content increases from 30% to 60%, the Ca(OH)2 content in SS-CPB hydration products decreases by 20.2%, and internal micropores increase. (4) When the SS content reaches 30%, the damage mode of SS-CPB changes from purely splitting failure to a plastic combination of splitting and shear failure. These research findings provide a new application model for the collaborative utilization of steel slag, tailings, and other solid wastes.

Mechanical damage characterization in human femoropopliteal arteries of different ages

Endovascular treatment of Peripheral Arterial Disease (PAD) is notorious for high failure rates, and interaction between the arterial wall and the repair devices plays a significant role. Computational modeling can help improve clinical outcomes of these interventions, but it requires accurate inputs of elastic and damage characteristics of the femoropopliteal artery (FPA) which are currently not available. Fresh human FPAs from n = 104 tissue donors 14–80 years old were tested using planar biaxial extension to capture elastic and damage characteristics. Damage initiation stretches and stresses were determined for both longitudinal and circumferential directions, and their correlations with age and risk factors were assessed. Two and four-fiber-family invariant-based constitutive models augmented with damage functions were used to describe stress softening with accumulating damage. In FPAs younger than 50 years, damage began accumulating after 1.51 ± 0.13 and 1.49 ± 0.11 stretch, or 196 ± 110 kPa and 239 ± 79 kPa Cauchy stress in the longitudinal and circumferential directions, respectively. In FPAs older than 50 years, damage initiation stretches and stresses decreased to 1.27 ± 0.09 (106 ± 52 kPa) and 1.26 ± 0.09 (104 ± 59 kPa), respectively. Damage manifested primarily as tears at the internal and external elastic laminae and within the tunica media layer. Higher body mass index and presence of diabetes were associated with lower damage initiation stretches and higher stresses. The selected constitutive models were able to accurately portray the FPA behavior in both elastic and inelastic domains, and properties were derived for six age groups. Presented data can help improve fidelity of computational models simulating endovascular PAD repairs that involve arterial damage. Statement of significanceThis manuscript describes inelastic, i.e. damage, behavior of human femoropopliteal arteries, and provides values for three constitutive models simulating this behavior computationally. Using a set of 104 human FPAs 14–80 years old, we have investigated stress and stretch levels corresponding to damage initiation, and have studied how these damage characteristics change across different age groups. Presented inelastic arterial characteristics are important for computational simulations modeling balloon angioplasty and stenting of peripheral arterial disease lesions.

Measurement and evaluation of the effect of vibration on fruits in transit—Review

Mechanical vibration is a prominent cause of produce damage in many postharvest fruit supply chains. Knowledge on the causes, occurrence, and mechanistic relationship of vibration to produce damage is important for systematic development of remedial actions. This review identifies and discusses the critical factors of vibration, their implications for fruit quality, and possible improvements to addressing the issue of fruit quality deterioration. Frequently reported mechanical damage types caused by vibration on fruits are scuffing, fruit rub, and skin bruising. A wide range of factors can significantly affect the vibration intensity and thus resultant mechanical damage. Critical frequencies of vibration in the range of 0 to 10 Hz, attributed to peak energy levels in the power spectrum, cause substantial damage in fruits. Greater vertical acceleration and transmission of vibration to the higher tiers in a stacked column of packages result in increased mechanical damage. Fruit packages stacked in the rear positions of trucks are also affected more by vibration. Produce transported in leaf spring trucks has a higher risk of damage when compared with air‐ride suspension trucks. Additionally increased road roughness, vehicle speed, and duration of exposure to vibration proliferate fruit damage. The effects of different inner packing methods and different package types on mechanical damage are less frequently investigated. More accurate characterization of mechanical damage caused by vibration and shocks and its reproduction by enhanced simulation methods will contribute to optimizing damage prevention mechanisms and further improving the quality of fruits in transit within the postharvest supply chain.

A new method for mechanical damage characterization in proppant packs using nuclear magnetic resonance measurements

Proppant performance can significantly affect the success of hydraulic fracturing treatments and production in unconventional plays. Performance of proppants can decrease rapidly by mechanical damage. Quantifying the impact of mechanical damage on proppant performance can be challenging either in the laboratory or in-situ condition. This paper introduces a new method based on Nuclear Magnetic Resonance (NMR) Transverse relaxation (T2) measurements to characterize pore-size distribution in proppant packs. Quantifying the pore-size distribution in proppant packs enables enhanced evaluation of porosity and conductivity of proppant packs and possible mechanical damage to the packs. The objectives of this paper are (a) to evaluate the performance of this new NMR-based method for characterizing pore structure of the proppant packs, and (b) to isolate and quantify the mechanical damage in proppant packs due to generating of fines in the laboratory using this new NMR-based method.First, we prepared proppant pack test samples in three categories including (a) different types of proppants with different surface relaxivity, (b) mixture of proppants with different sizes, and (c) proppants undergone different levels of mechanical damage. We measured NMR response in proppant packs and quantified the impacts of proppant type, size, and mechanical damage on NMR T2 distribution. Next, we used the fractional packing model to quantify the efficiency of packing of proppant mixture and to quantify the changes in porosity of proppant packs caused by variation in size and fraction of fines. Finally, we used Kozeny-Carman (KC) equation and modified Schlumberger Doll Research (SDR) equation to correlate the variation in T2 distribution to the decrease in proppant pack permeability.Results showed that NMR T2 distribution is sensitive to pore-size distribution in the proppant packs. The variable pore-size distribution was either a consequence of having a mixture of proppants with different sizes or different levels of mechanical damage. The impacts of fines on the pore-size distribution of the proppant packs was measureable, which is promising for the successful application of the introduced method for time-lapse quantification of generated fines. We also observed a measurable sensitivity of T2 distribution to mechanical damage in the proppant packs, which enables quantifying the level of damage in proppants through quantifying pore structure in the proppant packs. The NMR T2 measurements were, however, sensitive to the presence of paramagnetic materials such as iron in proppants. This sensitivity was more significant in cases where paramagnetic materials were distributed on the proppant surface. The proposed method is considered as an indirect measurement of pore structure and could potentially provide a quantitative assessment of the proppant pack conductivity both in the lab-scale and in-situ conditions. Improved assessment of proppant conductivity can help in enhancing the design and execution of fracture treatments for successful development of unconventional plays.

Mechanical-Damage Characterization in Proppant Packs by Use of Acoustic Measurements

SummaryThe strength and conductivity of proppant packs are key parameters for assessing proppant-pack performance. Mechanical damage in the propping agents, which leads to compaction and crushing, significantly reduces the conductivity of the proppant pack. Mechanical damage of proppants is usually analyzed by use of crush tests. However, measurements from these tests remain questionable because of discrepancies in procedures and test results. Therefore, a need emerges to develop techniques for characterizing the properties and mechanical damage in proppant packs.In this paper, we introduced a new technique that is based on interpretation of acoustic measurements from a granular effective-media model to quantify mechanical damage in propping agents. We performed uniaxial compression tests in the laboratory and measured the compressional- and shear-wave velocities in proppant packs loaded at axial stresses ranging from 10 to 110 MPa. After unloading the tests in which maximum axial stresses of 28, 55, 69, 97, and 110 MPa were applied, we conducted sieve analysis on the proppant packs. We applied an effective-medium theory modeled after the Hertz-Mindlin granular contact model to approximate the effective elastic properties. We then calibrated the model by use of the elastic properties estimated from the experimental measurements to characterize the mechanical damage of the proppant packs.We observed that the increase in grain-to-grain contact as the axial stress increases results in compaction and crushing in the proppant pack. We showed that the compaction effects and elastic and plastic behaviors in the stress–strain profile of the proppant pack were in agreement with the analysis of fines generated at different stress levels. The combined effect of compaction and crushing resulted in a reduction of porosity and, consequently, decreased the compressional- and shear-wave velocities of the proppant pack. The Hertz-Mindlin model showed a good approximation of the effective elastic properties estimated from the acoustic-wave velocities when calibrated with the pressure-dependent grain contact and the fraction of nonslipping grains as parameters. We demonstrated that the calibrated parameters can be correlated with the mechanical damage in the proppant pack. The characterization of mechanical damage in proppant packs can improve the design of the propping agents and quantification of proppant performance. Furthermore, the laboratory procedure can be extended to the use of borehole acoustic measurements in providing a real-time in-situ assessment of proppant performance.

Acoustic Measurements Aid Mechanical-Damage Characterization in Proppant Packs

This article, written by Special Publications Editor Adam Wilson, contains highlights of paper IPTC 18092, “Mechanical-Damage Characterization in Proppant Packs Using Acoustic Measurements,” by Aderonke Aderibigbe, SPE, Clotilde Chen Valdes, and Zoya Heidari, SPE, Texas A&M University, and Tihana Fuss, Saint-Gobain Proppants, prepared for the 2014 International Petroleum Technology Conference, Kuala Lumpur, 10–12 December. The paper has not been peer reviewed. The strength and conductivity of proppant packs are key parameters for assessing their performance. Mechanical damage of proppants usually is analyzed by crush tests. However, measurements from these tests remain questionable because of discrepancies in procedures and test results. This paper introduces a new technique based on interpretation of acoustic measurements to quantify mechanical damage in propping agents. Introduction Mechanical damage that leads to compaction and crushing is studied for sands by measuring ultrasonic velocities. Elastic properties can be estimated from compressional- and shear-wave velocities calculated from acoustic measurements. The elastic properties of unconsolidated sands usually are studied by use of effective-medium models for granular media. Effective- medium-theory approaches such as the Hertz- Mindlin model are often used to derive the effective elastic moduli of packings of identical and spherical granular materials. This model combines the Hertzian contact model, which is used to estimate the normal (compressional) stiffness for two identical spheres, and the Mindlin contact model, which is used to estimate the tangential (shear) stiffness of the spheres. Work investigating the relationship between the ratio of compressional- to shear-wave velocities and pressure as a result of preconsolidation and sorting in unconsolidated sands showed that the Hertz-Mindlin model overestimated the shear moduli and underestimated the pressure dependence of the moduli and the velocities of the unconsolidated sands when compared with experimental data from ultrasonic measurements. The discrepancy was attributed to the inability of the model to account for rotation of grains and slip at their boundaries. The work applied a modified Hertz-Mindlin model, in which it is assumed that there is no friction between the grains (hence, the tangential stiffness is negligible), to obtain a reasonable match between the model and experimental results. The disparities were attributed to the angularity of the sand grains and the assumption of no slip at the grain contacts. The disparities were modified by introducing an average- angularity parameter and assuming slip at the grain contacts. Previous publications documented applications of effective-medium models for assessment of elastic properties in rocks and unconsolidated sands. However, effective-medium models have not been applied in the assessment of elastic properties of proppant packs.

Mechanical damage characterization of glass fiber-reinforced polymer laminates by ultrasonic maps

A method for simultaneous measurement of the thickness and density for Glass Fiber-Reinforced Polymer (GFRP) laminate plates with ultrasonic waves in C-Scan mode is presented in the form of maps. The method uses three different signals in immersion pulse-echo C-Scan mode. The maps obtained based on the density show the heterogeneity of the material at high resolution at the pixel level (1×1mm2) and therefore they represent an efficient tool to assess and evaluate the damage of the composite structures after manufacturing and after an applied mechanical loading.

Characterization of mechanical damage in granite

This paper aims to illustrate the use of infrared thermography as a non-destructive and non-contact technique to observe the phenomenological manifestation of damage in granite under unconfined compression. It allows records and observations in real time of heat patterns produced by the dissipation of energy generated by plasticity. The experimental results show that this technique, which couples mechanical and thermal energy, can be used for illustrating the onset of damage mechanism by stress concentration in weakness zones.

Characterization of mechanical damage in coffee seeds by the LERCAFÉ test¹

The present work aimed at evaluating the use of the LERCAFE test to estimate germination and characterize mechanical damage in coffee seeds. The experiment was conducted in the Laboratory of Seed Research at the Universidade Federal de Vicosa, Vicosa-MG. Coffea arabica seeds were submitted to the following treatments: Lot 1 (0% of damaged seeds), Lot 2 (5% of damaged seeds), Lot 3 (10% of damaged seeds) and Lot 4 (15% of damaged seeds). The mechanical damage was caused with the use of the Pulverisette 14 (Fritsch) apparatus. The damage was caused randomly and individually in the seeds, and the lots proportionally combined undamaged and damaged seeds, totaling 1600 seeds per lot. The seeds were evaluated by the germination and LERCAFE tests. For this type of damage, the germination results achieved by the LERCAFE test presented high correlation with those achieved by the germination test (r=0,9550). Although being randomly caused in the seeds, in other words, without reaching a pre-determined region, the mechanical damage was always characterized by a breach in the embryo region and/or in the region opposite to the embryo and the edges of these breaches presented a green stain. The LERCAFE test was efficient to estimate germination and characterize mechanical damage in coffee seeds. Lots of seeds mechanically damaged presented a sharp decrease in the germination power

Characterization of mechanical damage on structural and electrical properties of silicon wafers

The effect of artificial mechanical damage in Czochralski silicon wafers was studied by measuring the structural and electrical characteristics of the wafers. A liquid honing method was used to induce mechanical damage and the damage grade was varied by controlling process parameters. Surface microroughness of the damaged sample was analyzed using an atomic force microscope (AFM). The wet oxidation/preferential etch method, photo-acoustic displacement (PAD) method and the minority carrier lifetime with a laser excitation/microwave reflection photoconductance decay technique were used to characterize the intensity of mechanical damage in silicon wafers. As the degree of mechanical damage increases, the density of oxygen induced stacking faults (OISF) is increased, while the depth of OISF generation is almost independent of damage grade. The minority carrier lifetime is inversely proportional to the mechanical damage grade, while the PAD values are proportionally increased. Other experimental results are discussed from a viewpoint of a structure–property relationship.