Investigation of the Biaxial Behaviour of 316 Stainless Steel Based on Critical Plane Method

In this work the biaxial behavior of 316 stainless steel is studied under the lens of critical plane approach. A series of ten experiments were developed on dog bone shape hollow cylindrical specimens made of type 316 stainless steel. Five different loading conditions were assessed, with (i) only axial stress, (ii) only hoop stress, (iii) proportional combination of axial and hoop stresses, (iv) non-proportional combination of axial and hoop stresses with square shape and (v) non-proportional combination of axial and hoop stresses with L-shape. The fatigue analysis is performed following four different critical plane theories, namely Wang-Brown, Fatemi-Socie, Liu I and Liu II. The efficiency of all four theories is studied in terms of the accuracy of their life predictions.

Investigating the challenges of measuring combination mechanics in textile fabrics

Measurements of the mechanical behavior of fabrics started during the Zeppelin era in the 1900s, where tensile, shear and biaxial behavior of the airship’s envelope fabric were measured. More measurement methods were developed later when there was a need to measure fabric handle and behavior. Although measurements of tensile, shear, buckling and bending have been established and are being used, their combinations, which represent a more realistic approach, are still being developed. However, these multi-axial measurements pose challenges not only in apparatus design but also in determining the measurement parameters. Here these challenges are being put forward and further research requirements are identified and discussed.

Dynamic Behavior of Cellular Materials under Combined Shear-Compression

A 3D cell-based finite element model is employed to investigate the dynamic biaxial behavior of cellular materials under combined shear-compression. The biaxial behavior is characterized by the normal stress and shear stress, which could be determined directly from the finite element results. A crush plateau stress is introduced to illustrate the critical crush stress, and the result shows that the normal plateau stress declines with the increase of the shear plateau stress, which climbs with the increase of loading angle. An elliptical criterion of normal plateau stress vs. shear plateau stress is obtained by the nonlinear regression method.

Abstract 368: Biomechanical Properties of Scar ECM: from the Acute to Chronic Stages of Myocardial Infarction

Introduction: Myocardial infarction (MI) affects more than 8 million Americans, causing massive heart cell death and heart function decrease. To better understand the scar biomechanics, we characterized the mechanical properties of pure scar ECM, obtained by decellularizing the MI tissues. Materials and Methods: Infarcted rat hearts were generated by a permanent left coronary artery ligation (PLCAL) and harvested at 15 min, 1, 2, and 4 weeks (per acute to chronic stages of MI)(N = 6 each). Scar ECM were obtained by decellularizing the infarcted hearts in 0.1% sodium dodecyl sulfate (SDS) solution for 3 weeks. Scar ECM specimens were trimmed into square shape, and then subjected to biaxial testing with one edge aligned with the circumferential direction and the other edge aligned with the longitudinal direction of the rat heart. After 10 cycle preconditioning, an equibiaxial tension protocol of T circ : T rad = 30:30 N/m was performed to capture the tissue biaxial behavior. Results and Discussion: Scar ECM 15 minutes through 4 weeks post infarction showed a stiffening biaxial behavior along with the time (Fig.1). The decrease of extensibility along longitudinal direction was more noticeable than circumferential direction, which led to a decrease in degree of anisotropy. Conclusions: Scar ECM biomechanics showed a stiffening behavior with a marked reduction in extensibility (longitudinal) with time. This change in biomechanical properties can be correlated to the collagen structure changes with progression of MI. Knowledge of the structural-mechanical relationship of scar ECM will help us understand MI progression and help formulate regenerative therapies.