Teaching Design and Strength of Materials via Additive Manufacturing Project-Based Learning

Additive manufacturing of an Fe–Cr–Ni–Al maraging stainless steel: Microstructure evolution, heat treatment, and strengthening mechanisms

We perform a comparison study on characteristic regimes in shocked porous materials whose mechanical properties cover a wide range. Via the Minkowski functional analysis, it is found that different materials may show the same fractional size of characteristic regimes in the shock-loading procedure, even if one uses the same threshold value to define those regimes. Characteristic regimes in the material with larger initial yield are more dispersed. For a fixed shock strength, there exists a material strength with which the shock wave reaction contributes the maximum plastic work. With the decreasing of shock strength, this material strength becomes smaller. These observations may present helpful indications for new material designs.

In helping students learn engineering design, it is very important that they explore complex scenarios that are realistic, and fall outside the domain of standard and over-simplified textbook problems that typically have an answer. A majority of the current educational methods and computer-based tools do not bridge this gap and lack affordances for design exploration. Although computational methods such as Finite Element Analysis have this potential, they are hard to use requiring the users to spend a significant effort. Also, several instructors have identified significant knowledge gaps in concepts related to structural design and strength of materials when the students reach their senior year. To this end, we have developed a problem-based framework to allow for rapid design exploration within engineering design curricula using an easy-to-use, simplified and constrained version of finite elements for stress analysis and exploration. Our framework makes it possible for users to rapidly explore various design options by incorporating a Finite Element Analysis (FEA) backend for design exploration. Our approach uses a constrained design problem for weight minimization that incorporates elements of structural topology optimization but does not automate it. Instead we provide the user the control on decision making for changing the shape through material removal. Using this framework, we explore the decision making of users, and their methodology in the course of the activities that provide a context of control, challenge and reflection. Using video and verbal protocol analysis we integrate assessment in ways that are important and interesting for learning. Our framework demonstrates that the ability of computational tools that are transformed for learning purposes can scaffold and augment learning processes in new ways.

A variety of image generation methods have emerged in recent years, notably DALL-E 2, Imagen and Stable Diffusion. While they have been shown to be capable of producing photorealistic images from text prompts facilitated by generative diffusion models conditioned on language input, their capacity for materials design has not yet been explored. Here, we use a trained Stable Diffusion model and consider it as an experimental system, examining its capacity to generate novel material designs especially in the context of 3D material architectures. We demonstrate that this approach offers a paradigm to generate diverse material patterns and designs, using human-readable language as input, allowing us to explore a vast nature-inspired design portfolio for both novel architectured materials and granular media. We present a series of methods to translate 2D representations into 3D data, including movements through noise spaces via mixtures of text prompts, and image conditioning. We create physical samples using additive manufacturing and assess material properties of materials designed via a coarse-grained particle simulation approach. We present case studies using images as starting point for material generation; exemplified in two applications. First, a design for which we use Haeckel’s classic lithographic print of a diatom, which we amalgamate with a spider web. Second, a design that is based on the image of a flame, amalgamating it with a hybrid of a spider web and wood structures. These design approaches result in complex materials forming solids or granular liquid-like media that can ultimately be tuned to meet target demands.

Strain-stiffening--an increase in material stiffness at large strains--is a vital mechanism by which many soft biological materials thwart excessive deformation to protect tissue integrity. Understanding the fundamental science of strain-stiffening and incorporating this concept into the design of metals and ceramics for advanced applications is an attractive prospect. Using cementite (Fe3C) and aluminium borocarbide (Al3BC3) as prototypes, here we show via quantum-mechanical calculations that strain-stiffening also occurs, surprisingly, in simple inorganic crystalline solids and confers exceptionally high strengths to these two solids, which have anomalously low resistance to deformation near equilibrium. For Fe3C and Al3BC3, their ideal shear strength to shear modulus ratios attain remarkably high values of 1.14 and 1.34 along the (010)[001] and slip systems, respectively. These values are more than seven times larger than the original Frenkel value of 1/2π (refs 4, 5) and are the highest yet reported for crystalline solids. The extraordinary stiffening of Fe3C arises from the strain-induced reversible 'cross-linking' between weakly coupled edge- and corner-sharing Fe6C slabs. This new bond formation creates a strong, three-dimensional covalent bond network that resists large shear deformation. Unlike Fe3C, no new bond forms in Al3BC3 but stiffening still occurs because strong repulsion between Al and B in a compressed Al-B bond unsettles the existing covalent bond network. These discoveries challenge the conventional wisdom that large shear modulus is a reliable predictor of hardness and strength of materials, and provide new lessons for materials selection and design.

Chapter 6 - Design, performance, and mechanism of cement-based materials with 2D nanomaterials

Glasses are materials that lack a crystalline microstructure and long-range atomic order. Instead, they feature heterogeneity and disorder on superstructural scales, which have profound consequences for their elastic response, material strength, fracture toughness, and the characteristics of dynamic fracture. These structure-property relations present a rich field of study in fundamental glass physics and are also becoming increasingly important in the design of modern materials with improved mechanical performance. A first step in this direction involves glass-like materials that retain optical transparency and the haptics of classical glass products, while overcoming the limitations of brittleness. Among these, novel types of oxide glasses, hybrid glasses, phase-separated glasses, and bioinspired glass-polymer composites hold significant promise. Such materials are designed from the bottom-up, building on structure-property relations, modeling of stresses and strains at relevant length scales, and machine learning predictions. Their fabrication requires a more scientifically driven approach to materials design and processing, building on the physics of structural disorder and its consequences for structural rearrangements, defect initiation, and dynamic fracture in response to mechanical load. In this article, a perspective is provided on this highly interdisciplinary field of research in terms of its most recent challenges and opportunities.

Selected results and initiatives in modern asphalt pavement research for increasing service life of asphalt pavements under the aspect of sustainability and multifunctional use of roads are summarized. Focus lies on innovative approaches and own experience, jointly elaborated during the last decades within the road engineering/sealing components lab at Empa and both the highway/railways engineering and building materials group at KTH. This includes material concepts and design as well as pavement system and construction aspects from an experimental and modelling point of view. It includes also the application of powerful experimental and computational tools, such as Atomic-Force-Microscopy (AFM), X-Ray-Computer-Tomography (CT), Digital-Imaging-Correlation (DIC) and Discrete-Element-Method (DEM). As for materials, recycling issues and the use of Phase-Change-Materials (PCM) or metallic ingredients for inductive thermal crack healing are addressed. In order to remind that material design must also account for the workability during the process of compaction, the new Compaction-Flow-Test (CFT) developed at KTH is shortly presented. Innovative ideas for structural material composition are also mentioned, such as “artificial aggregates” or “additive manufacturing”, being aware that there is still a long way to go. Regarding pavement systems, ideas for multifunctional road applications are proposed. Focus is also put on special issues, such as construction joints.

In the present work, we are concerned with heterogeneous material systems that have multiple distinct materials and void phases, and associated interfaces, for which the geometric scale and specific morphology at the micro/nano-level play an essential role in the global properties, functional behavior, and material system performance. Such materials are at the heart of revolutionary advances in devices that convert and store energy (e.g., batteries, fuel cells, solar cells, capacitors, and many electro-optical devices), and other membrane-based devices used in chemical and fuel processing, sequestration, and extraction. In recent years, advances in a variety of additive manufacturing methods and techniques have made it possible to design, control, and fabricate specific micro- or nano-structure to achieve prescriptive functional performance of the material systems and devices in which they appear. However, systematic multiphysics analysis methods properly set on field equations that represent the local details is not available, so that first-principles understandings and designs of those materials are not properly founded. Recently, the doe established an energy frontiers research center for physics based nanostructure design and fabrication of heterogeneous functional materials, called the HeteroFoaM center, to address this and related questions. The present paper presents some initial findings of part of that effort related specifically to morphology. For the present study, a finite element model (FEM) was developed Using COMSOL MULTIPHYSICS to predict impedance behavior when the field equations are set on the local features of regular geometric micro-structures The results for are compared with experimental data obtained from impedance spectroscopy of single SOFC fuel cell elements. For the model, equivalent idealized geometric structures were assumed corresponding to the YSZ material morphology of the fuel cell. Continuously aligned pore structures were represented by rectangular extrusions and regular porosity was represented by geometric shapes such as circles, rectangles and triangles. For experimental data, fragments of a button cell were used with silver paste contacts on the electrodes. For the model, the geometric microstructure was varied by using different shapes i.e. circles, rectangles and triangles while keeping the total material quantity constant, and by using equivalent areas for each of the geometric shapes. Impedance response for the frequency range from 1Hz to 1MHz was obtained for both the models and the experiments. Observations and interpretations of morphology effects are presented.

Purpose: The purpose of this work is to analyses the behavior and mechanical properties of metals, alloys, polymers, concrete, and composites of various materials at low and cryogenic temperatures below 123 K (-150.15°C). This review paper highlights the influence of cryogenic conditions upon material selection and design for applications where critical service conditions require exposure to extreme cold, including energy storage, aerospace, offshore structures, superconducting technologies, shipbuilding, and LNG carriers. Design/methodology/approach: This review attempts to synthesize results from experimental studies, computational modeling, and theoretical analyses that have examined changes in material mechanical properties at cryogenic conditions. This review is focused on the fracture toughness, tensile strength, brittleness, and associated properties of the various classes of materials. In so doing, the approach is aimed at understanding how those properties evolve at low temperatures and their implications on materials selection and design for harsh environment applications. Findings: Results show that even though cryogenic temperatures can be applied to enhance the tensile strength, modulus, ultimate strength, and fatigue resistance of materials, they simultaneously cause a significant reduction in ductility, therefore making the material more brittle with enhanced susceptibility to micro-cracking. The paper underlines the fact that material development should proceed to develop those possessing increased strength, resistance to wear and corrosion with less compromise of ductility. Limitations/implications of the research: The complexity in testing materials at cryogenic conditions and the difficulty in directly correlating the experimental results with real applications are the limitations of the research. Further research is needed before such challenges are met and before materials with optimum performance at low temperatures, without sacrificing key properties, are developed. Originality/value: This review gives important insight into the mechanical behavior of materials at cryogenic temperatures and points out the need for advanced material development with specific emphasis on additive manufacturing for tailoring material properties in view of superior performance and reliability in extreme cryogenic environments. The results will be an important guideline for future research and material selection of various industries, specifically aerospace and energy storage.

Strength, ductility and superplasticity of microcrystalline two-phase materials

Core-shell structured Si@Cu nanoparticles segregated in graphene-carbon nanotube networks enable high reversible capacity and rate capability of anode for lithium-ion batteries

A simulation study of the effects of membrane structure parameters on dehumidification performance of membrane-based liquid dehumidifier

Limited test data hinder the accurate prediction of mechanical strength and permeability of permeable cement-stabilized base materials (PCBM). Here we show a kriging-based surrogate model assisted artificial neural network (KS-ANN) framework that integrates laboratory testing, mathematical modeling, and machine learning. A statistical distribution model was established from limited test data to enrich the dataset through the combination of markov chain monte carlo simulation and kriging-based surrogate modeling. Subsequently, an artificial neural network (ANN) model was trained using the enriched dataset. The results demonstrate that the well-trained KS-ANN model effectively captures the actual data distribution characteristics. The accurate prediction of the mechanical strength and permeability of PCBM under the constraint of limited data validates the effectiveness of the proposed framework. As compared to traditional ANN models, the KS-ANN model improves the prediction accuracy of PCBM’s mechanical strength by 21%. Based on the accurate prediction of PCBM’s mechanical strength and permeability by the KS-ANN model, an optimization function was developed to determine the optimal cement content and compaction force range of PCBM, enabling it to concurrently satisfy the requirements of mechanical strength and permeability. This study provides a cost-effective and rapid solution for evaluating the performance and optimizing the design of PCBM and similar materials.

This study systematically investigates the effects of varying Cl−/SO42− concentration ratios in saline solutions on the drying shrinkage, mechanical properties, and microstructure evolution of a cementitious system under simulated saline–alkali conditions. The underlying influence mechanism is elucidated via TG-DTG, XRD, and SEM analyses. Experimental results indicate that increasing the Cl−/SO42− concentration ratio of the mixing water from 0.2 to 2.5 leads to a significant rise in early-age drying shrinkage, with an increase of approximately 19%, while it simultaneously enhances the early-age compressive strength of the cementitious matrix, achieving increases of approximately 13% at 1 d, 14% at 3 d, 14% at 7 d, and stabilizing at about 7% by 28 d. Microscopic characterizations reveal that as the Cl−/SO42− concentration ratio increases, the ettringite content decreases, the contents of Friedel’s salt and calcium hydroxide increase, and the cementitious microstructure accordingly becomes denser. This work aims to provide theoretical and experimental references for the durability design and performance optimization of cement-based materials in saline–alkali regions.