Effects of Shape and Orientation of Pore Canals on Mechanical Behaviors of Lobster Cuticles

The work is to investigate the relationships between the microstructures and mechanical behaviors of lobster cuticles and reveal the inner mechanisms of the anisotropic mechanical properties of the cuticles and give the helpful guidance for the design of high-performance man-made composites. First, the tensile mechanical properties of the longitudinal and transverse specimens of the cuticles of American lobsters were tested with a mechanical-testing instrument. It is was found that the fracture strength and elastic modulus of the longitudinal specimens are distinctly larger than those of the transverse specimens. Then, the microstructural characteristics of the fracture surfaces of the specimens were observed with scanning electron microscope. It was observed that the pore canals in the cuticles are elliptic and their orientations are along the longitudinal orientation of the cuticles. Furthermore, the stresses and micro-damage of the longitudinal and transverse specimens were calculated with the rule of progressive damage by finite element method. It was revealed that the shape and orientation of the pore canals in the cuticles give rise to the anisotropic mechanical property of the cuticles and ensure that the cuticles possess the largest fracture strength and elastic modulus along their largest main-stress orientation.

Study on the Mechanical Property of 20Cr13 Stainless Steel Barrel Processed by Cold Radial Forging

The barrel is a key part of automatic weapon. And the cold radial forging progress is a new technology for manufacturing the barrels. It will introduce some changes of the material, such as increased strength, decreased plasticity and introduction of anisotropic mechanical property. It can affect the service performance, so it is necessary to study the difference of tangential and axial mechanical properties of barrel blank and forged barrel. This paper focuses on the research of 20Cr13 stainless steel barrel. The mechanical properties of barrel blank and forged barrel are measured by the tensile, compression and bulging test. And the hardness is measured by Vickers hardness tester. The structural change of 20Cr13 stainless steel also has been observed by metalloscope in the metallographic experiment. It reveals the influence of the cold radial forging progress on the mechanical properties of 20Cr13 stainless steel barrel. And it also provides the reference data of the cold radial forging progress of 20Cr13 stainless steel.

Tailoring Plate-Like Grained ZrB2 Ceramic via a Strong Magnetic Field Alignment Method Followed by Spark Plasma Sintering

Through strong magnetic field alignment (SMFA) method followed by spark plasma sintering (SPS), dense tailored ZrB2 ceramic could be prepared using the plate-like grains as initial material. The measured Lotgering orientation factor f(00l) on the textured top surface (TTS) was high as 0.62 and f(hk0) on the textured side surface (TSS) was 0.65. Vickers hardness measurement showed the anisotropic mechanical property of textured sample. On the TTS, the hardness was 13.4 ± 0.9 GPa, while on the TSS the hardness was 12.0 ± 0.9 GPa.

Development of Numerical Tool for Analysis of Microstructural Fracture Behavior in Smart & Intelligent Materials

As a numerical tool for examining the microstructural fracture behavior in the smart and intelligent materials, a finite element method with the interface element was developed and the applicability of this method was studied through the serial computations using virtual polycrystalline models. As the results assuming the influence of grain orientation on the grain boundary, it was found that the anisotropic mechanical property of grain boundary (interaction between opening and slipping deformations) would be a dominant factor of the fracture process. Also, by employing the theory of crystal plasticity for the mechanical property of grain, it was revealed that the stress concentrations caused by both the mismatch between neighbor grains and the slipping at grain boundary could be demonstrated by using this method.