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The paper aims to shed some light on the effect of the notch/crack‐tip stresses and their role on the cyclic plasticity and crack growth behavior in compression‐compression fatigue.

Compression precracking was studied using 2D finite element analysis for CT specimen. The final crack length and the shape of the crack front were compared with those obtained experimentally.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. Only the internal stress corresponding to P_max shows a significant redistribution with the crack extension whereas the stress corresponding P_min is not affected by the increase of crack length.

This results are limited to Mode I cracking.

It supports that two thresholds, ΔK^th and K_max^th, govern the fatigue crack behavior. When the contribution from the internal tensile stress is not big enough to make K_max exceed K_max^th the crack will self arrest.

It has been found that cyclic plasticity and stress redistribution govern the observed fatigue crack growth behavior in compression‐compression precracking. The comparison of the numerical results with experimental data in terms of final crack length and crack front shape indicated a fair agreement.

The purpose of this paper is to describe the effects of stress ratio (R) on the threshold stress intensity factor range (ΔKth) by applied overload and to conduct an analytical investigation of the effect of the stress ratio.

Tensile overload was applied to a compact tension specimen, and fatigue tests were performed at R=0.1 or 0.5.

The value of ΔK_th increased as the tensile overload was increased, and the nominal threshold values were given by the equation Δ^NK_th,R = C+ DK_ov, where C represents ΔK_th, and D is a proportional constant. Experimental results showed that the value of D showed good agreement with theoretical value.

The paper proposes a new model that arrests crack growth or makes cracks harmless by utilizing the overload effect.

The current study mainly focuses on the effect of varying diameter recycled steel fibers (RSF) on mechanical properties of concrete prepared with 25 and 50% of recycled coarse aggregate (RCA) as well as 100% natural aggregate (NA). Two types of RSF with 0.84 mm and 1.24 mm diameter having 30 mm length were incorporated into normal and recycled aggregate concrete (RAC).

The fresh behavior, compressive, splitting tensile, flexural strengths and modulus of elasticity of all the mixes were investigated to evaluate the mechanical properties of RACs. In addition, specimen crack and testing co-relation were analyzed to evaluate fiber response in the RAC.

According to the experimental results, it was observed that mechanical properties decreased with the increment replacement of NA by RCA. However, the RSF greatly improves the mechanical properties of both normal concrete and RACs. Moreover, mixes containing 1.24 mm diameter RSF had a more significant positive impact on mechanical properties than mixes containing 0.84 mm diameter RSF. The 0.84 mm and 1.24 mm RSF addition improved the mixes' compressive, splitting tensile and flexural strength by 10%–19%, 19%–30% and 3%–11%, respectively when compared to the null fiber mix. Therefore, based on the mechanical properties, the 1.24 mm diameter of RSF with 25% replacement of RCA was obtained as an optimum solution in terms of performance improvement, environmental benefit and economic cost.

The practice of RCA in construction is a long-term strategy for reducing natural resource extraction and the negative ecological impact of waste concrete.

This is the first study on the effects of varying size (0.84 mm and 1.24 mm diameter) RSF on the mechanical properties of RAC. Additionally, varying sizes of RSF and silica fume added a new dimension to the RAC.

Topologically interlocked materials are a class of materials in which individual unit elements interact with each other through contact only. Cracks and other defects occurring due to external loading are contained in the individual unit elements. Thus, topologically interlocked materials are damage tolerant and provide high structural integrity. The purpose of this paper is to investigate the concepts of remanufacturing in the context of a material for which the intended use is structural such that the material's structural integrity is of concern. In particular, the study is concerned with the mechanical behavior of a topologically interlocked material.

A topologically interlocked material based on tetrahedron unit elements is investigated experimentally. Manufacturing with aid of a robotically controlled end‐effector is demonstrated, and mechanical properties are determined for a plate configuration. A conceptual mechanical model for failure of topologically interlocked materials is developed and used to interpret the experimental results.

It is demonstrated that remanufacturing of the topologically interlocked material is possible with only a limited loss of material performance. The proposed model predicts trends in agreement with the experimental findings.

While the model predictions are qualitatively in agreement with experiments, more detailed finite element models are needed to predict the material performance accurately. Experiments were conducted on a model material obtained from a 3D printer and should be verified on other solids.

The authors demonstrate that damage containment together with the absence of binders or adhesives enables reuse through remanufacturing without loss of structural integrity.

Topologically interlocked materials emerge as attractive materials for sustainable engineering once their material performance are weighted with an environmental impact factor.

Remanufacturing experiments on a novel class of materials were conducted and a new model for the characterization of the structural integrity of topologically interlocked materials is proposed and successfully evaluated against experiments in at least qualitative form.

Interviews over 120 sellers and low‐level distributors of the drug “crack” in New York City. Documents seller strategies to counter police tactics. Finds that crack sellers and distributors have developed several important strategies to limit vulnerability to arrest, but that success in avoiding arrest diminishes considerably once they are detected by police. Suggests that problem‐oriented approaches are better than crackdowns, since they permanently disrupt the environmental conditions that foster drug market sites.

This paper aims to explore the design and fabrication of meso-scale Manufacturing Process-Driven Structured Materials (MPDSMs). These are designed, architected materials where the prime design requirement is manufacturability. The concepts are applied to those fabricated using fused deposition modeling or fused filament fabrication (FDM/FFF), a thermoplastic polymer additive manufacturing (AM) process. Three case studies were presented to demonstrate the approach.

The paper consists of four main sections; the first developed the MPDSMs concept, the second explored manufacturability requirements for FDM/FFF in terms of MPDSMs, the third presented a practical application framework and the final sections provided some case studies and closing remarks.

The main contributions of this study were the definition and development of the MDPSMs concept, the application framework and the original case studies. While it is most practical to use a well-defined AM process to first explore the concepts, the MPDSMs approach is neither limited to AM nor thermoplastic polymer materials nor meso-scale material structures. Future research should focus on applications in other areas.

The MPDSMs approach as presented in this concept paper is a novel method for the design of structured materials where manufacturability is the prime requirement. It is distinct from classic design-for-manufacturability concepts in that the design space is limited to manufacturable design candidates before the other requirements are satisfied. This removes a significant amount of schedule and costs risk from the design process, as all the designs produced are manufacturable within the problem tolerance.

Extends the notion of informality into the area of illegality, looking at how illegal crack vendors in New York use informality to reduce and pass risk to others. Focuses on the techniques used to avoid detection and arrest and the methods of placing risk of imprisonment on smaller, lower‐income dealers. Suggests that this process of exploitation only makes sense when seen in the broader context of inequality in US society where some have nothing to lose by going to jail.

In this chapter, I examine how racial disparities in punishment for nonviolent drug crimes align with significant differences in how the black and white drug problems are constructed in media, law enforcement, and academia.

By examining differences in how the black and white drug problems have been constructed over the past 70 years for the opioids (heroin, prescription painkillers), cocaine (both powder and crack), and marijuana, I illustrate how these distinct representations of the black and white drug problems accompany more punitive policies in response to black drug epidemics even as white drug epidemics are typically met with tolerance or indifference.

Historically, powerful interest groups like media and law enforcement have benefitted from circulating myths and exaggerations about the illegal drug problem that encourage punitive drug policies. By contrast, at least some academics have benefitted from taking the opposite tack and debunking many of these myths. Unfortunately, academics have been less willing to challenge myths about the black drug problem than the white drug problem. Indeed, some academics actually reinforce many of the myths about the black drug problem promoted by media and law enforcement.

This chapter builds upon a substantial academic literature that challenges myths about illegal drug use by whites. However, it goes beyond this literature to consider the paucity of similar academic research exposing media and law enforcement myths about the black drug problem.

The purpose of this paper is to find the response of micro‐layered rapid prototyping material under impact loading.

A modified Hopkinson Bar was used to impart impact loading in velocities ranging from 2‐7 m/s. Strain gages and stress wave theory were employed to calculate the load‐point force and displacement. Hence the dynamic crack initiation and propagation energies were calculated.

It was found that the crack deflection and inter layer delamination mechanisms lead to greater absorption of crack propagation energy and hence offer better resistance to crack propagation as compared to monolithic acrylonitrile butadiene styrene (ABS).

The finding will lead to greater confidence for the use of rapid prototypes as direct‐use parts subjected to low velocity impact.

Although the static properties of ABS material used in rapid prototyping are well documented, this paper is one of the first reported researches in measuring the impact response of the micro layered ABS.