Osteocytes and mechanical loading: The Wnt connection

Bone adapts to the mechanical forces that it experiences. Orthodontic tooth movement harnesses the cell‐ and tissue‐level properties of mechanotransduction to achieve alignment and reorganization of the dentition. However, the mechanisms of action that permit bone resorption and formation in response to loads placed on the teeth are incompletely elucidated, though several mechanisms have been identified. Wnt/Lrp5 signalling in osteocytes is a key pathway that modulates bone tissue's response to load. Numerous mouse models that harbour knock‐in, knockout and transgenic/overexpression alleles targeting genes related to Wnt signalling point to the necessity of Wnt/Lrp5, and its localization to osteocytes, for proper mechanotransduction in bone. Alveolar bone is rich in osteocytes and is a highly mechanoresponsive tissue in which components of the canonical Wnt signalling cascade have been identified. As Wnt‐based agents become clinically available in the next several years, the major challenge that lies ahead will be to gain a more complete understanding of Wnt biology in alveolar bone so that improved/expedited tooth movement becomes a possibility

Loading Surface in the Course of Mechanical- Thermal Treatment and Steady-State Creep of Metals

Abstract: Kinetics of the loading surface of a material gives precious information on the level of the hardening of the material. This paper is concerned with the evolution of the loading surface during successive actions, such as: (i) plastic deformation, (ii) annealing of the pre-strained specimen, and (iii) secondary creep of the treated material. The analysis of the loading surface is carried out in terms of the synthetic theory of irrecoverable deformation. Keywords: loading surface; mechanical-thermal treatment; creep and plastic strain; synthetic theory of irrecoverable deformatio

Combined mechanical loading of composite tubes

An analytical/experimental investigation was performed to study the effect of material nonlinearities on the response of composite tubes subjected to combined axial and torsional loading. The effect of residual stresses on subsequent mechanical response was included in the investigation. Experiments were performed on P75/934 graphite-epoxy tubes with a stacking sequence of (15/0/ + or - 10/0/ -15), using pure torsion and combined axial/torsional loading. In the presence of residual stresses, the analytical model predicted a reduction in the initial shear modulus. Experimentally, coupling between axial loading and shear strain was observed in laminated tubes under combined loading. The phenomenon was predicted by the nonlinear analytical model. The experimentally observed linear limit of the global shear response was found to correspond to the analytically predicted first ply failure. Further, the failure of the tubes was found to be path dependent above a critical load level

Pre-fatigue influence on quasi-static tensile properties of Ti-6Al-4V in thin-sheet form

The response of engineering structures to loads is most often assessed without taking possible damage of the used material(s) into account. However, it has already been proved that a preceding cyclic loading and the alteration of the microstructure it causes, can have a significant influence on the mechanical properties of steel grades and aluminium alloys , and hence on the behaviour of structural elements made of it. Ti-6Al- 4V, the most widely used titanium alloy, is often one of the materials chosen for cyclic loading applications where other solicitations are present too. Therefore, the influence of pre-fatigue on the quasi-static mechanical properties of Ti-6Al-4V in thin-sheet form is investigated. Tensile experiments are performed on samples subjected to different damage levels. The material does not show a clear dependence of its tensile properties with previous loading cycles, although the overall effect can be important for particular geometries

Projection-based measurement and identification

A recently developed Projection-based Digital Image Correlation (P-DVC) method is here extended to 4D (space and time) displacement field measurement and mechanical identification based on a single radiograph per loading step instead of volumes as in standard DVC methods. Two levels of data reductions are exploited, namely, reduction of the data acquisition (and time) by a factor of 1000 and reduction of the solution space by exploiting model reduction techniques. The analysis of a complete tensile elastoplastic test composed of 127 loading steps performed in 6 minutes is presented. The 4D displacement field as well as the elastoplastic constitutive law are identified. Keywords: Image-based identification, Model reduction, Fast 4D identification, In-situ tomography measurements. INTRODUCTION Identification and validation of increasingly complex mechanical models is a major concern in experimental solid mechanics. The recent developments of computed tomography coupled with in-situ tests provide extremely rich and non-destructive analyses [1]. In the latter cases, the sample was imaged inside a tomograph, either with interrupted mechanical load or with a continuously evolving loading and on-the-fly acquisitions (as ultra-fast X-ray synchrotron tomography, namely, 20 Hz full scan acquisition for the study of crack propagation [2]). Visualization of fast transformations, crack openings, or unsteady behavior become accessible. Combined with full-field measurements, in-situ tests offer a quantitative basis for identifying a broad range of mechanical behavior.Comment: SEM 2019, Jun 2019, Reno, United State

Mechanical coupling for high cyclic loading

One-piece cylindrical coupling with ""necked-down'' regions at each end form flexures allowing small misalignments between actuator and load. Coupling has zero backlash, low mass, close spacing between actuator and load, high stiffness in direction of motion, and allowance for misalignments and deflections without causing high side loading on components

Static and Dynamic Thermomechanical Buckling Loads of Functionally Graded Plates.

In the paper the buckling phenomenon for static and dynamic loading (pulse of finite duration) of FGM plates subjected to simultaneous action of one directional compression and thermal field is presented. Thin, rectangular plates simply supported along all edges are considered. The investigations are conducted for different values of volume fraction exponent and uniform temperature rise in conjunction with mechanical dynamic pulse loading of finite duration