Influence of the preheating on the microstructure evolution within thick deposits of AISI M4 high speed steel processed by Laser-DirectedEnergy Deposition, based on thermal modelling, hardness characterization, and dilatometry tests

editorial reviewedThe AISI HSS M4 alloy that contains many strong carbide forming elements is a medium carbon tool steel which is among the most ones that have been proceed under additive manufacturing. It has been well established that preheating is required to obtain sound and crack-free parts when both L-PBF and L-DED processes are considered. However, little is known about the evolution of the microstructure during the manufacturing process. This work is based on the comparison of HHS M4 L-DED thick deposits cladded on a AISI 4140 steel substrate, which has been preheated following three different routes: a preliminary preheating within a furnace, a continuous induction preheating, and a preheating using laser beam. The microstructure of the deposits is characterized via macro and nano hardness profiles. Then a validated thermal model is used to reconstruct the thermal histories within the deposit during laser processing, and the final structure obtained in each deposit is linked to the temperature evolution. Based on adequate dilatometry tests, a discussion on the influence of step thermal gradients on solid phase transformations is carried out.IAWATHA - InnovAtion en WAllonie par les TecHnologies Additive

Microstructure prediction in additive manufacturing(TA6V, AlSi10Mg, AISI M4 materials)

Bilan des travaux depuis 3 ans sur 3 matériaux en additive manufacturin

Reactor physics project progress report

Statement of responsibility on title page reads: Editors: M.J. Driscoll and T.J. Thompson; Contributors: F.M. Clikeman, J.N. Donohew, M.J. Driscoll, J.D. Eckard, T.L. Harper, Y. Hukai, I. Kaplan, C.H. Kim, Y.-M. Lefevre, T.C. Leung, N.R. Ortiz, N.C. Rasmussen, C.S. Rim, S.S. Seth, A.T. Supple C. Takahata, and T.J. Thompson"MIT-3944-1."Progress report; September 30, 1968U.S. Atomic Energy Commission contract AT(30-1)-394

31st Annual Meeting and Associated Programs of the Society for Immunotherapy of Cancer (SITC 2016) : part two

Background The immunological escape of tumors represents one of the main ob- stacles to the treatment of malignancies. The blockade of PD-1 or CTLA-4 receptors represented a milestone in the history of immunotherapy. However, immune checkpoint inhibitors seem to be effective in specific cohorts of patients. It has been proposed that their efficacy relies on the presence of an immunological response. Thus, we hypothesized that disruption of the PD-L1/PD-1 axis would synergize with our oncolytic vaccine platform PeptiCRAd. Methods We used murine B16OVA in vivo tumor models and flow cytometry analysis to investigate the immunological background. Results First, we found that high-burden B16OVA tumors were refractory to combination immunotherapy. However, with a more aggressive schedule, tumors with a lower burden were more susceptible to the combination of PeptiCRAd and PD-L1 blockade. The therapy signifi- cantly increased the median survival of mice (Fig. 7). Interestingly, the reduced growth of contralaterally injected B16F10 cells sug- gested the presence of a long lasting immunological memory also against non-targeted antigens. Concerning the functional state of tumor infiltrating lymphocytes (TILs), we found that all the immune therapies would enhance the percentage of activated (PD-1pos TIM- 3neg) T lymphocytes and reduce the amount of exhausted (PD-1pos TIM-3pos) cells compared to placebo. As expected, we found that PeptiCRAd monotherapy could increase the number of antigen spe- cific CD8+ T cells compared to other treatments. However, only the combination with PD-L1 blockade could significantly increase the ra- tio between activated and exhausted pentamer positive cells (p= 0.0058), suggesting that by disrupting the PD-1/PD-L1 axis we could decrease the amount of dysfunctional antigen specific T cells. We ob- served that the anatomical location deeply influenced the state of CD4+ and CD8+ T lymphocytes. In fact, TIM-3 expression was in- creased by 2 fold on TILs compared to splenic and lymphoid T cells. In the CD8+ compartment, the expression of PD-1 on the surface seemed to be restricted to the tumor micro-environment, while CD4 + T cells had a high expression of PD-1 also in lymphoid organs. Interestingly, we found that the levels of PD-1 were significantly higher on CD8+ T cells than on CD4+ T cells into the tumor micro- environment (p < 0.0001). Conclusions In conclusion, we demonstrated that the efficacy of immune check- point inhibitors might be strongly enhanced by their combination with cancer vaccines. PeptiCRAd was able to increase the number of antigen-specific T cells and PD-L1 blockade prevented their exhaus- tion, resulting in long-lasting immunological memory and increased median survival

Static and dynamic mechanical response of different cork agglomerates

Cork is a natural cellular material capable of withstanding considerable amounts of energy and exhibiting a viscoelastic return to its original shape. This feature is particularly interesting to resist to successive impacts. In this study, the behavior of different types of agglomerated cork (AC) and expanded cork (EC) is investigated under static and dynamic loadings. Double impact was carried out on the samples using a hemispheric actuator. The peak acceleration data for all compounds were further analyzed. Static compression tests gave an interesting insight into the stress–strain curve of agglomerates and Poisson’s ratio variation during deformation. Results demonstrate a clear influence of agglomerated density and grain size on the resulting mechanical properties and point out a tremendous potential for this sustainable material to be tailored to fit diverse crashworthiness applications

Comparing the mechanical performance of synthetic and natural cellular materials

his work compares the mechanical performance of agglomerated cork against synthetic materials typ- ically used as impact energy absorbers. Particularly, the study will focus on the expanded polystyrene (EPS) and expanded polypropylene (EPP). Firstly, quasi-static compression tests are performed in order to assess the energy storage capacity and to characterize the stress–strain behavior cellular materials under study. Secondly, guided drop tests are performed to study the response of these materials when subjected to multiple dynamic loading (two impacts). Thirdly, finite element analysis (FEA) is carried out in order to simulate the compressive behav- ior of the studied materials under dynamic loading. Results show that agglomerated cork is an excellent alternative to the synthetic materials. Not only for being a natural and sustainable material but also for withstanding considerable impact energies. In addi- tion, its capacity to keep some of its initial properties after loading (regarding mechanical properties and dimensions) makes this material highly desirable for multiple-impact applications

A 2D and 3D thermal model of powder injection laser cladding

Thermal 2D and 3D finite element models were elaborated to retrieve the high temperature gradients generated during multi-layer laser cladding deposition. The model can deliver the complete thermal history of the deposition process. Convection and radiation phenomena were taken into account. Key points from the specimen had their temperature evolution saved with thermocouples during the production and used later to calibrate the numerical model. The method to compute the heat input in the 2D model once the 3D model has been validated is described. An accurate thermal history of the specimens is the first step to predict crack by thermo-mechanical model and microstructure by thermo-metallurgical model.PDR Laser Claddin

3-D finite element analysis of laser cladding process. Application to Ti-6Al-4V

In this study, a 3-D thermal numerical modelling of laser cladding by powder injection as a repair technology applied to Ti-6Al-4V was developed. In order to implement the movement of the heat source in the model and the addition of material, a C++ programme was developed. Transition refinement elements are used to reduce the number of degrees of freedom. The temperature distribution and its time evolution were computed which allowed the prediction of the heat affected zone and the fusion size of the substrate. Effects of heat source distribution, energy input are investigated. Temperature measurements validate the model