Assessment of the Level of Quality Control of Cement and Sandcrete Block Materials Available in Maiduguri Metropolis

The variation of incoming material properties and the quality of emerging advanced high-strength steels significantly increases the costs for product design and production. It is not economical to tightly control material chemistry to eliminate the variation of material properties at steel mills. This paper introduces a methodology on how to implement a non-destructive evaluation (NDE) tool to measure the variation of the incoming material properties. The servo-controlled forming process was successfully optimized to adapt to variations in the incoming material properties in a lab-scale stamping cell with a 300-Ton mechanical servo press. Final stamping quality was obtained with three different batch materials by altering servo press parameters, such as the slide motion and blank holder force, to adjust for the variation of the material properties from one batch to another. Both a mid-strength (340-MPa tensile strength) steel and a high-strength steel (980-MPa tensile strength) were evaluated in this study. The study shows the effectiveness of an NDE tool to non-destructively measure the sheet material properties and the servo-press control to adjust the press parameters for the variation of the material properties.

<p>A series of influential papers in the 1980’s showed how the long-term evolution of fold-and-thrust belts and accretionary wedges (here collectively termed orogenic wedges) can quantitatively be described as striving towards a mechanical equilibrium defined by their internal and basal material strengths (Dahlen 1984, Dahlen et al. 1984, Davis et al. 1983). Unstable orogenic wedges will deform to adjust their basal and surface slopes to a critical taper angle, defined by a wedge that is at the verge of failure everywhere. Critical taper theory has been confirmed by analogue and numerical experiments and found numerous successful applications in field studies.</p><p>The success of critical taper theory forms a framework that allows investigating non-critical behaviour of orogenic wedges. Previous numerical and analogue studies pointed out that: (1) Only portions of orogenic wedges may be at failure at any given time, separating critically stressed from non-critical segments (Lohrmann et al. 2003, Simpson 2011). As these wedges still observe a critical taper, this may indicate that it is the critically stressed segments that define the overall wedge shape. (2) Numerical experiments often attain a critical taper at lower shortening percentages than analogue experiments. We speculate that this may be related to larger amounts of strain softening generally used in numerical setups and/or the number of shear zones that forms at equivalent shortening (which is controlled by numerical resolution and analogue material properties). This non-criticality is thus likely only a transient state.</p><p>We here ask the question whether structural inheritance from earlier compressional or extensional deformation phases may lead to longer-term non-critical wedge behaviour by favouring out-of-sequence thrusting or shear zone propagation into the foreland. To address this question, we combine a review of previous dynamic wedge experiments with new analogue experiments that investigate the influence of inherited shear zones and variations in material properties on wedge evolution. We shorten quartz sand layers overlying a weak basal microbeads layer with a non-deformable backstop. The backstop has two independently moving parts, allowing to alternate thin- and thick-skinned deformation. We find that the reactivation of basement shear zones formed in earlier deformation phases is short-lived and does not affect thrusting to a degree that would distinguish these wedges from those without inheritance. We extend these experiments by including variations in internal material properties and weaker shear zones, remaining however in the domain of brittle orogenic wedges.</p><p>Non-critical wedge behaviour may only be a transient state, but could occur frequently owing to variations in material properties or structural inheritance, which are to be expected in regions of inter-plate shortening of former rift regions. Our contribution hopes to highlight the potential for future modelling studies of orogenic wedges to examine how non-critical wedge behaviour could play into the evolution of fold-and-thrust belts and accretionary wedges.</p>

Traumatic brain injury (TBI) is a major health challenge, is very difficult to diagnose, and currently has no accepted treatment options. The difficulty in diagnosis is due to the complex pathophysiology of TBI, where the damage mechanisms span multiple spatial and temporal scales and ultimately manifest as diverse cognitive impairments in brain function. The speed and dynamic nature with which the mechanical insults occur in TBI means that computational models are the best candidate to mimic the in vivo event and to investigate the injury progression in detail. A current weakness in TBI computational models is the poor understanding of how material properties within different regions of the brain change after damage. Here, we developed an animal experiment pipeline where a controlled and reproducible mechanical insult can be applied to a sheep brain in vivo followed by ex vivo compression mechanical testing. For each brain, the compression mechanical testing was conducted across the length of the brain to assess baseline regional variations in material properties and how these properties changed after mechanical impact. Using this pipeline, we have characterized locational variations in the brain material properties both pre and post‐TBI. Our preliminary results confirm that there exist locational variations in the brain material properties across all regions of cerebrum. The analysis of post‐TBI tissues showed that compressive strength was reduced in the area nearest the direct impact.

In the Nigerian construction industry, sandcrete block is an important building material, it is used in the construction of the building and other useful physical infrastructure. Many of the sandcrete blocks are produced at different locations and environment using different aggregate materials without resort to the minimum quality standard expected of the sandcrete block. It is on this bases that the study assessed the quality of sandcrete block produced with river sand in order to determine their compliance level to the standard expected of a sandcrete block in Nigeria. Eighteen sandcrete blocks of size 225 mm × 225 mm × 450 mm were gotten from three different production locations in Ifo, Ogun State Nigeria. Sieve analyses, bulk density, silt content, and the compressive test were carried out to determine the property quality of aggregate material (river sand) used for the production of the blocks and its strength. The result shows that the aggregate material used was of good quality suitable for the production of the sandcrete block. The result also shows that the average compressive strength of 1.16 N/mm2 for sandcrete blocks from different production sites does not meet up with the minimum requirement for sandcrete block compressive strength as stipulated by NIS 2007 and ISO 848492-1994. The study revealed that the quality of the block produced is not affected by the quality of aggregate used but by poor quality control of aggregate and other materials used in the production of the blocks. It further revealed that the block quality is also affected by shoddy/improper curing of blocks produced. The study, therefore, concluded that regulatory and professional bodies should organize seminars for the local producers of sandcrete blocks on the best practice of producing quality blocks in meeting the required quality standard for construction work to avoid structural cracks and collapsing of building.KeywordsSandcrete blockSieve analysisBulk densitySilt contentCompressive strength

The general design approach in the Mechanistic-Empirical pavement Design Guide (MEPDG) is to compare the performance of several trail structures over the design period against previously defined performance criteria to choice the best alternative after life cycle and constructability analyses. The material properties are selected from laboratory testing, correlation or typical values depending on the hierarchical levels deÆ ned by the designers. Layers in a flexible pavement structure are built with different materials and different asphalt mix types. The MEPDG predicted performance of pavement structures varies with variations of the material properties and material properties combination in the different layers. The effect on pavement performance from variations of material properties in the different layers of a pavement structure is analyzed in this study using MEPDG. The study showed that results from sensitivity studies of MEPDG to material properties can be used in selection of pavement materials for better performance.

Clinical and experimental studies have shown the masticatory complex (the skeletal and soft tissues associated with feeding) to be phenotypically plastic with regard to dietary material properties. Harder, tougher diets generally produce larger skeletal elements with greater bone density. However, less is known about the plasticity of the chewing musculature. Muscles are composed of two primary fiber types: slow‐twitch (type I) and fast‐twitch (type II). Fast‐twitch fibers produce rapid, powerful contractions but fatigue more quickly than slow‐twitch fibers. Here we use a rodent model to examine the plasticity of the masseter muscle fibers in response to inter‐individual variation in dietary material properties. We hypothesize that rats raised on hard, tough diets will have more fast‐twitch muscle fibers with greater cross‐sectional area, representing an increase in force production by the masseter in response to the dietary material properties.Male Sprague‐Dawley rats were raised from weaning (3 weeks) to adulthood (16 weeks) in two dietary treatment groups: a “hard/tough” pellet diet and a “soft” meal diet. Post‐sacrifice, fixed muscles were embedded in paraffin and divided into anterior, middle, and posterior regions. To visualize fast‐twitch fibers, 6 sections per region per individual were stained with a primary antibody for the fast isoforms of myosin heavy chain (MHC) and a fluorescent secondary antibody. Images were collected at 4× using a fluorescent confocal microscope. ImageJ was used to collect total muscle cell area, fast‐twitch cell area, and slow‐twitch and fast‐twitch cell counts. Mann‐Whitney U tests were used to compare cell count and area between the treatment groups (n=5/group, α = 0.05).Preliminary results indicate that hard/tough diets tend to be associated with a decrease in slow‐twitch fiber count and an increase in fast twitch fiber cross‐sectional area in the rat masseter. This allows for a greater proportion of fast‐twitch muscle fibers in a given muscle volume. We propose that this change reflects an increase in muscle force production during feeding on mechanically challenging food items. The results of this study allow for greater understanding of skeletal muscle growth postnatally through adulthood, and provides insight into the consequences of material properties of diet for the function and dysfunction of the human masticatory complex. Future studies are needed to address how muscle fiber plasticity changes with age and with intra‐individual variation in the material properties of diet.Support or Funding InformationFunding was provided by the NSF (BCS‐1061368), the Wenner‐Gren Foundation, the American Society of Mammalogists, and the American Association for Anatomy Innovations Program.

An effective multilayered sandwich beam-link finite element for solution of the electro-thermo-structural problems

Cervical spinal injuries are a significant concern in all trauma injuries. Recent military conflicts have demonstrated the substantial risk of spinal injury for the modern warfighter. Finite element models used to investigate injury mechanisms often fail to examine the effects of variation in geometry or material properties on mechanical behavior. The goals of this study were to model geometric variation for a set of cervical spines, to extend this model to a parametric finite element model, and, as a first step, to validate the parametric model against experimental data for low-loading conditions. Individual finite element models were created using cervical spine (C3–T1) computed tomography data for five male cadavers. Statistical shape modeling (SSM) was used to generate a parametric finite element model incorporating variability of spine geometry, and soft-tissue material property variation was also included. The probabilistic loading response of the parametric model was determined under flexion-extension, axial rotation, and lateral bending and validated by comparison to experimental data. Based on qualitative and quantitative comparison of the experimental loading response and model simulations, we suggest that the model performs adequately under relatively low-level loading conditions in multiple loading directions. In conclusion, SSM methods coupled with finite element analyses within a probabilistic framework, along with the ability to statistically validate the overall model performance, provide innovative and important steps toward describing the differences in vertebral morphology, spinal curvature, and variation in material properties. We suggest that these methods, with additional investigation and validation under injurious loading conditions, will lead to understanding and mitigating the risks of injury in the spine and other musculoskeletal structures.

Product defect compensation by robust optimization of a cold roll forming process

Robust processes and robust engineering are enjoying increasing interest throughout industry. Robust engineering is taking into account variations that can occur during manufacturing processes when we analyse or optimise them. Corus is interested in robust engineering, being a supplier of steel not just for its own processes but also for supporting customers. Robust engineering, if properly applied to e.g. the stamping process, ensures that the customer’s forming process is stable and insensitive to material and process variations, thus reducing scrap rates. To analyse a stamping process for robustness input in terms of variation in process and material properties is needed. As a material supplier we focus on the variation in material properties. This paper deals with the effect of the material models used in simulation on the prediction of process variations as well as scrap rate. The effect of models on the variation itself is small, however, the effect on the average (and hence on e.g. scrap rate) is significant. Some examples of the capabilities of commercial software are also added.

ABSTRACTThis paper investigates the effect of a variation in material properties on the crack tip opening displacement, a parameter often used in the prediction of fatigue and fracture. This situation is typical when a component is subjected to a relatively slow temperature fluctuation or the material properties undergo direct changes, such as due to a phase transformation. An analytical strip‐yield model is developed using the small‐scale yielding assumption and theory of complex potentials. Four cases of crack tip plasticity behaviour are identified for the different combinations of parameters controlling the variation in material properties. Results of calculations over a wide range of material properties are presented and show a significant effect on the crack tip opening displacement. Finite element simulations are conducted to verify the analytical findings. The implications of the outcomes in relation to several practical situations are also discussed.

We have carried out static compression tests in the poling direction for PZT ceramics and evaluated the material properties by measuring the resonance and anti-resonance frequencies and electrostatic capacity at regular intervals. Then the variation in the material properties up to fracture was clarified. Also, the development of internal damage was also clarified quantitatively by evaluating a damage variable on the basis of the continuum damage mechanics. The damage variable was calculated from the ratio of the elastic coefficient to its initial value. In the present paper, the development of internal damage was formulated as an evolution equation of the damage variable. In the formulation, a threshold stress leading to the onset of damage was considered. Moreover, the variation in material properties was related to the damage variable and formulated as material functions of the damage variable. The development of internal damage and the variation in material properties were simulated by the equations proposed in the present paper and the validity of the equations was verified by comparing the predictions with experimental results.

Target strength model inputs including morphometry, material properties, lipid composition, and in situ orientations were measured for sub-Arctic krill (Euphausia pacifica, Thysanoessa spinifera, T. inermis, and T. raschii) in the eastern Bering Sea (EBS, 2016) and Gulf of Alaska (GOA, 2017). Inter-species and -regional animal lengths were significantly different (F1,680 = 114.10, p < 0.01), while animal shape was consistent for all species measured. The polar lipid phosphatidycholine was the dominant lipid, comprising 86 ± 16% (mean ± SD) and 56 ± 22% of total lipid mass in GOA and EBS krill, respectively. Krill density contrasts varied by species and region rather than with morphometry, lipid composition, or local chla fluorescence. Mean in situ krill orientation was 1 ± 31°, with 25% of observed krill within ±5° of broadside incidence. Modelled target strength sensitivity was frequency independent for variations in material properties but was primarily sensitive to morphometry and orientation at lower (38 kHz) and higher (200 kHz) frequencies, respectively. Measured variability in material properties corresponded to an order of magnitude difference in acoustic estimates of biomass at 120 kHz. These results provide important inputs and constraints for acoustic scattering models of ecologically important sub-Arctic krill species.

Physics-Informed Uncertainty Quantification in Modeling of Machining-Induced Residual Stress

Guided-wave-based acousto-ultrasound structural health monitoring (SHM) methods have attracted the interest of the SHM community as guided wave scan travel long distances without significant dissipation and are capable of detecting small damage sizes of several types. However, when subject to changing environmental and operational conditions (EOC), guided-wave-based methods may give false indications of damage as they exhibit increased sensitivity to varying EOC. In order to improve the reliability and enable the large-scale applicability of these methods, and to build a robust SHM system, it is necessary to quantify the uncertainty in guided wave propagation due to changing EOC. In this paper, a rigorous investigation on the uncertainty involved in the propagation of Lamb waves due to the variation in temperature and material properties of nominally-identical structures has been performed both numerically and experimentally. A high fidelity finite element model is established to study the effect of small temperature perturbation on the S0 and A0 modes of Lamb waves and the associated uncertainty is quantified. Then experiments are performed under ambient laboratory temperature variations during an eleven day period. The experimental results have indicated that temperature variations as small as 0.5 0C may result variations in the amplitude of Lamb waves and affect the damage index. Then uncertainty due to the variation in material properties has been considered by taking into account the statistical Gamma distributed dependency between Young’s modulus and Poisson ratio jointly and the associated variation in the damage index is also investigated.