Development Of A Biaxial Testing Apparatus

<div>Material testing is a crucial part of engineering design and development, especially in aerospace engineering as it is more cost effective to test an element or component than doing a full-scale test on the completed part. Typically, uniaxial testing is carried out to characterize a material,</div><div>which is adequate for finding the properties of the material. However, these kinds of tests are inadequate for simulating the real-world loading that a component may experience in its life cycle. Therefore, this project’s goal was to develop a low-cost biaxial testing apparatus using off-the-shelf components, including the Arduino Uno microcontroller (“Arduino”), stepper motors (“motors”), and load cell. This report outlines the development of the software required to</div><div>operate the motors and read output value of the load cell. The Arduino code used to control the motors was developed using open-source code available on GitHub and the Stepper library, which contains the required functions for controlling the motors. The Arduino code can be used</div><div>to determine the strain rate of up to 11 𝑚𝑚/𝑚𝑖𝑛, as well as the type of loading (tension or compression) along each axis. </div>

Development Of A Biaxial Testing Apparatus

<div>Material testing is a crucial part of engineering design and development, especially in aerospace engineering as it is more cost effective to test an element or component than doing a full-scale test on the completed part. Typically, uniaxial testing is carried out to characterize a material,</div><div>which is adequate for finding the properties of the material. However, these kinds of tests are inadequate for simulating the real-world loading that a component may experience in its life cycle. Therefore, this project’s goal was to develop a low-cost biaxial testing apparatus using off-the-shelf components, including the Arduino Uno microcontroller (“Arduino”), stepper motors (“motors”), and load cell. This report outlines the development of the software required to</div><div>operate the motors and read output value of the load cell. The Arduino code used to control the motors was developed using open-source code available on GitHub and the Stepper library, which contains the required functions for controlling the motors. The Arduino code can be used</div><div>to determine the strain rate of up to 11 𝑚𝑚/𝑚𝑖𝑛, as well as the type of loading (tension or compression) along each axis. </div>

Sheep Sclera Soft Tissue Subjected to Mechanical Equi-Biaxial Testing

A better understanding of diseases progress in tissues vest on the accurate understanding of tissues under mechanical loading. Also, development of therapies for injuries may depend on the available mechanical data for soft tissues. In this study, the raw data of biaxial tensile testing of sclera soft tissue is presented in this paper. Biaxial mechanical testing of soft tissues presents details understanding of how soft tissues behave when compared to uniaxial testing. Biomechanical properties of soft tissues are vital in the development of accurate computational models. Reliable computational models of studying mechanisms of diseases depends mainly on the accurate and more details mechanical behavior of soft tissues. These accurate and detailed computational models may be utilized to further develop the understanding and therapies of various diseases. The mechanical tensile testing was conducted on the passive sheep sclera. Engineering stress vs strain of several samples of the sheep sclera are further presented determined from force and displacement experimental data. The goal of this paper is to make available biaxial data of sheep sclera soft tissue that can be further utilized.

From Uniaxial Testing of Isolated Layers to a Tri-Layered Arterial Wall: A Novel Constitutive Modelling Framework

Mechanical testing and constitutive modelling of isolated arterial layers yields insight into the individual layers’ mechanical properties, but per se fails to recapitulate the in vivo loading state, neglecting layer-specific residual stresses. The aim of this study was to develop a testing/modelling framework that integrates layer-specific uniaxial testing data into a three-layered model of the arterial wall, thereby enabling study of layer-specific mechanics under realistic (patho)physiological conditions. Circumferentially and axially oriented strips of pig thoracic aortas (n = 10) were tested uniaxially. Individual arterial layers were then isolated from the wall, tested, and their mechanical behaviour modelled using a hyperelastic strain energy function. Subsequently, the three layers were computationally assembled into a single flat-walled sample, deformed into a cylindrical vessel, and subjected to physiological tension-inflation. At the in vivo axial stretch of 1.10 ± 0.03, average circumferential wall stress was 75 ± 9 kPa at 100 mmHg, which almost doubled to 138 ± 15 kPa at 160 mmHg. A ~ 200% stiffening of the adventitia over the 60 mmHg pressure increase shifted layer-specific load-bearing from the media (65 ± 10% → 61 ± 14%) to the adventitia (28 ± 9% → 32 ± 14%). Our approach provides valuable insight into the (patho)physiological mechanical roles of individual arterial layers at different loading states, and can be implemented conveniently using simple, inexpensive and widely available uniaxial testing equipment.

An Investigation into the Correlation of Small Punch and Uniaxial Creep Data for Waspaloy

Within the aerospace sector, the understanding and prediction of creep strains for materials used in high-temperature applications, such as Nickel-based super alloys, is imperative. Small punch testing offers the potential for understanding creep behavior using much less material than conventional uniaxial testing but in contrast to uniaxial creep tests, the stress in small punch creep (SPC) tests is multiaxial. SPC testing can be a valuable tool for validating models of creep deformation, but the key to unlocking its full capability is through the accurate correlation of the creep material properties measured through both techniques. As such, the focus of this paper is to correlate the creep behavior of Waspaloy obtained through conventional uniaxial testing to that obtained via small punch creep testing. Recently, and for low chrome steels, this has been achieved through use of the ksp method, but there are good reasons for believing this technique will not work so well for Nickel-based super alloys. This paper shows this to be the case for Waspaloy and proposes some alternative methods of correlation based on combining the Monkman–Grant relation and the Wilshire equations for both uniaxial and small punch creep. It was found that this latter approach enabled the accurate conversion of SPC minimum displacement rates to equivalent uniaxial minimum creep rates which, when combined with the Wilshire equations, enabled SPC test loads to be converted into equivalent uniaxial stresses (and visa versa) with levels of accuracy that were significantly reduced when compared to using the ksp method. Further, the random error associated with these conversions were dramatically increased.

Material modelling of FDM printed PLA part

This paper focuses on modelling inelasticity of additively manufactured polylactide (PLA) thermoplastic using Fused Deposition Modelling (FDM) printing technology. The material response of PLA is viscoplastic and temperature-dependent, as is typically seen for thermoplastics. The inelastic deformation of printed PLA undergoes initial yielding, strain softening, and subsequent failure. The Three-Network (TN) constitutive model was employed in this work, which captures experimentally observed material response and consists of three molecular equilibrium and time-dependent viscous networks that act in parallel. The parameter identification was performed in accordance with experimental data from uniaxial testing and a validation experiment was carried out by loading plate with a hole and measuring its strain distribution using Digital Image Correlation (DIC) method, which was compared with the predictions from Finite Element Analysis (FEA).

Deterioration of Glutaraldehyde Crosslinked Heterograft Biomaterials due to Advanced Glycation End Product Formation and Serum Albumin Infiltration

ABSTRACTBioprosthetic heart valves (BHV) are fabricated from glutaraldehyde cross-linked heterograft tissue, such as bovine pericardium (BP) or porcine aortic valves. BHV develop structural valve degeneration (SVD), often with calcification, requiring BHV replacement. Advanced glycation end products (AGE) are post-translational, non-enzymatic carbohydrate protein modifications. AGE are present in SVD-BHV clinical explants and not detectable in unimplanted BHV. Here, we studied the hypothesis that BHV susceptibility to AGE formation and serum protein infiltration results in deterioration of both leaflet collagen structure and mechanical properties. In vitro experiments studied BP and porcine collagen sponges (CS) for susceptibility to AGE formation using 14C-glucose and 14C-glyoxal with and without bovine serum albumin (BSA), as a model serum protein. The results showed AGE formation is a rapid and progressive process. BSA co-incubations reduced glyoxal and glucose uptake by BP and CS. Incubating BP in BSA caused a substantial increase in BP mass, enhanced by glyoxal co-incubation. Per two-photon microscopy, BP with AGE formation and BSA infiltration each induced significant disruption in collagen microarchitecture, with loss of collagen alignment and crimp. These effects are cumulative with the greatest disruption occurring when there was both AGE formation and BSA infiltration. Uniaxial testing of CS demonstrated that AGE formation, together with BSA uptake compared to controls, caused a significant deterioration in mechanical properties with a loss of viscoelastic relaxation and increased stiffness. It is concluded that AGE-BSA associated collagen structural disruption and deterioration of mechanical properties contribute to SVD.

Nonlinear, dissipative phenomena in whole blood clot mechanics

We use uniaxial testing to quantify nonlinear, dissipative mechanisms in whole blood clot mechanics.