The development of computational models to describe bone behavior when prosthetic devices are used has gained tremendous importance. In particular, computational modeling for bone growth and resorption processes can be a useful tool to determine the implant success or failure. We present a model for investigating bone density growth for healthy and prosthetic femur with a total hip arthroplasty. The model, which is based on a continuum theory for density growth and remodeling in biological materials that accounts for the coupling between biological and mechanical effects, is implemented in COMSOL Multiphysics and two simulation examples are presented. In the first example, where mechanical loads due to daily physical activities are considered, it is shown that higher stress zones (in prosthetic femur mid-diaphysis of about 46 MPa) and lower stress zones (in prosthetic femur neck of about 28 MPa) are candidates for bone growth and resorption zones, respectively. In addition, it is shown that higher and lower stress levels in these zones may lead to possible periprosthetic fractures (bone mid-diaphysis overloaded in 7-10 MPa post-operatively) and eventually to implant aseptic loosening due to resorption (bone femoral neck unloaded in 13-17 MPa post-operatively). In the second example, where the mechanical load corresponds to the average of the loads considered previously, the obtained results for bone density are in good agreement with real bone density distribution in the proximal femur, which illustrates the model capability to locate bone density growth zones (of about 1615 kg=m 3 in the mid-diaphysis) and bone density resorption zones (of about 1259 kg=m 3 in the neck) due to mechanical loads for the femur post-operative condition after a total hip arthroplasty surgical procedure.

The computational modeling of instrumented indentation tests used to characterize material properties is challenging. It is mainly due to the computational techniques demanded to couple the complex physical mechanisms involved, such as, for example, the time-dependent inelastic material response to loads during contact. Therefore, this work aims to simulate the mechanical response of the poly vinylidene fluoride (PVDF) during a micro-indentation test considering a viscoplastic material model, and a prescribed load approach, using the finite element method. Further, model validation is performed based on experimental data measured during the contact between the indenter and the PVDF. Numerical analyses were performed using COMSOL Multiphysics finite element software considering the loading scheme of the experimental tests of 800 mN/ min rate during loading and unloading, and a 400 mN constant load, held by 30 s. Finally, a viscoplastic Chaboche constitutive model is presented considering two cases: (1) a perfectly plastic behavior, and (2) a nonlinear isotropic hardening behavior based on Voce and Hockett-Sherby exponential laws. While the latter models exhibit some discrepancy in capturing the experimental behavior, the former one has shown excellent agreement with the load-depth curves obtained experimentally, achieving the best fitting for the set of Chaboche parameters: A = 1 s −1 , n = 4.62 and ref = 132 MPa. Moreover, several phenomenological features of viscoplastic behavior such as rate dependence, plastic flow (or creep) and stress relaxation were accurately provided by the Chaboche model when describing the behavior of the PVDF material. Keywords Viscoplasticity • Polymers • Microindentation • Finite elements Nomenclature E Young's modulus F y Yield function h max Maximum indentation depth h r Residual or final indentation depth h m , r m PVDF sample thickness and radius J 2 Second deviatoric stress invariant P Applied load P max Maximum applied load Q p Plastic potential r i Indenter radius S Deviatoric stress tensor t h Holding load time vpe Effective viscoplastic strain vp Viscoplastic strain tensor Cauchy's stress tensor Mises Effective von Mises stres ys Yield Stress ys0 Initial yield stress sat , Voce model parameters Technical Editor: João Marciano Laredo dos Reis.

Professor in Woodstock College, Maryland.Having learned that a collection of cuneiform inscriptions had arrived at the Metropolitan Museum of Art, New York, I visited the Museum during the month of August, 1884, to examine the new collection and to practice copying the cuneiform contract tablets at the east end of the building.Among the valuable pieces of the new collection was a cuneiform Babylonian Cylinder. Upon expressing a wish to copy it, I was informed it could be done only on two conditions. The first was the permission of General L. P. di Cesnola, Director of the Museum; the second was the permission of the owner of the collection, as it was not yet Museum property. With kindly courtesy, facility for study and the privilege of copying the Cylinder was granted by the Director of the Museum. Mr. Bernard Maimon, the actual owner and original collector, also consented with the restriction that no publication should be made until the pur-