Penetration mechanics of elongated female and male genitalia of earwigs

We unveiled the penile penetration mechanics of two earwig species, Echinosoma horridum, whose intromittent organ, termed virga, is extraordinarily long, and E. denticulatum, whose virga is conversely short. We characterised configuration, geometry, material and bending stiffness for both virga and spermatheca. The short virga of E. denticulatum has a material gradient with the stiffer base, whereas the long virga of E. horridum and the spermathecae of both species are homogeneously sclerotised. The long virga of E. horridum has a lower bending stiffness than the spermatheca. The virga of E. denticulatum is overall less flexible than the spermatheca. We compared our results to a previous study on the penetration mechanics of elongated beetle genitalia. Based on the comparison, we hypothesised that the lower stiffness of the male intromittent organ comparing to the corresponding female structure is a universal prerequisite for the penetration mechanics of the elongated intromittent organ in insects.

Investigation of the penetration behavior of silicon dioxide epoxy hybrid nanocomposites

The use of nanomaterials is gradually increasing with the progress of nanotechnology. In particular, the production of nanocomposites incorporating nanoparticles is one of the most significant areas in which nanomaterials are being used increasingly. The first objective of this research was to detect the punch shear or penetration resistance behavior and damage mechanisms of hybrid nanocomposites obtained by using silica (SiO2) nanoparticles. For that purpose, six different SiO2 hybrid nanocomposites with different laminations three layer (3La), 5La, 7La, 11La, 15La and 21La and different thicknesses (HC) of 0.95∼4.98 mm, were made by using vacuum assisted transfer molding (VARTM). During this research, quasi-static punch-shear (QS-PS) tests at span punch ratios (SPRs) of 1.16, 1.33, 1.67, 2.00, 2.33, 2.67, and more were conducted to determine quasi-static penetration mechanics and penetration resistance behavior. Moreover, deflection, energy dissipation, damage area, stiffness, and peak force values were investigated through experimental results and scanning electronic microscope (SEM) images.

Ultra-sensitive measurement of brain penetration mechanics and blood vessel rupture with microscale probes

Microscale electrodes, on the order of 10-100 μm, are rapidly becoming critical tools for neuroscience and brain-machine interfaces (BMIs) for their high channel counts and spatial resolution, yet the mechanical details of how probes at this scale insert into brain tissue are largely unknown. Here, we performed quantitative measurements of the force and compression mechanics together with real-time microscopy for in vivo insertion of a systematic series of microelectrode probes as a function of diameter (7.5–100 μm and rectangular Neuropixels) and tip geometry (flat, angled, and electrochemically sharpened). Results elucidated the role of tip geometry, surface forces, and mechanical scaling with diameter. Surprisingly, the insertion force post-pia penetration was constant with distance and did not depend on tip shape. Real-time microscopy revealed that at small enough lengthscales (<25 μm), blood vessel rupture and bleeding during implantation could be entirely avoided. This appears to occur via vessel displacement, avoiding capture on the probe surface which led to elongation and tearing for larger probes. We propose a new, three-zone model to account for the probe size dependence of bleeding, and provide mechanistic guidance for probe design.

A comment on “Constant deceleration approach for the penetration analysis of rigid projectiles into concrete targets: Revisited” by D.Z. Yankelevsky and V.R. Feldgun, Int. J. Prot. Struct., pp. 1–18 (2020)

The purpose of this Comment is to highlight several inaccuracies in the recently published paper of Yankelevsky and Feldgun, which criticizes our work on concrete penetration. The main subject of their criticism concerns our treatment of the entrance phase in concrete penetration, and we show here that their claims are inaccurate and misleading. We do not engage in the existing debates concerning different approaches to the penetration mechanics of rigid projectiles.

EXPLICIT FORMULA FOR DEPTH OF PENETRATION OF CONE-NOSED IMPACTOR INTO ANISOTROPIC SHIELDS

The field of application of Functionally Graded Materialsis steadily expanding, which stimulates research in the relevant areas. In relation to penetration mechanics, these are primarily experimental studies of multilayer barriers consisting of plates “in contact” with various mechanical properties. Despite intensive research, explicit formulas for integral penetration characteristics (penetration depth and ballistic limit) cannot be obtained, except for the case when sequential penetration of layers (barriers with large gaps between layers). In this article, explicit formulas for the depth of penetration into an semi-infinite shield and for the ballistic limit velocity applying penetration into a shield of a finite thickness are derived assuming that the hardness of the barrier material varies continuously depending on barrier depth. The theoretical analysis is based on a model that represents the normal stress at points on the surface of the penetrating body that are in contact with the barrier as a quadratic function of the normal component of local impactor velocity with a zero linear term (the Vitman - Stepanov model). Difference of the dynamic hardness in different points of impactor-barrier contact is taken into account. It is also assumed that the nose of the striker has the form of a straight circular cone and the initial stage of penetration when the striker is not completely immersed in the barrier is ignored.