Preface

Since time immemorial, man has needed to protect himself from the inclemency of nature; this justified the construction of a living place. Constructions that were erected based on empirical rules, which were transmitted from generation to generation verbally and, for which there was no scientific treatise or research that defined a study of the behavior of the materials used in its construction. Great structures carried out in different cultures can be mentioned; the Egyptians built great temples, pyramids (2778-2160 BC) and obelisks; the Chinese built the Great Wall of China (3rd century BC) and fortified cities, and the Aztecs created their great cities.

The Greeks advanced the art of construction, known as the study of the "determination of the centers of gravity" by Archimedes (287-212 BC), whose theory was used for the transport and lifting of the columns of the Temple of Diana of Ephesus. With the birth and development of the Roman Empire, the Romans became great builders, as a result, we have the great coliseums and the famous Pont du Gard in southern France. The Greeks and Romans accumulated experience for many years in the art of structural engineering, which had a little boom during the Middle Ages and was only expressed strongly during the Renaissance. The Italian architect Fontana (1543-1607), who built the Vatican obelisk at the request of Pope Sixtus V, is famous from this time.

During the renaissance, the contributions made by Leonardo Da Vinci (1452-1519) are highlighted in his notes "Testing the strength of iron wires of various lengths" and apparently performed research about column loads, which stated that "the load varies inversely with the length and directly with the cross-section." Also, Leonardo was the first to draw the catenary and propose a study using a discrete model, which was a great contribution to the resistance of materials. Galileo Galilei in his book "Discorsi e dimostrazioni matematiche intorno a due nuove scienze", shows methods applied to the analysis of stresses where he presents a logical sequence of analysis. The "two new sciences" that the Galilean text alludes to are the "Strength of Materials", which he addresses in the first two chapters of the book. The other science is that of the "Local Movement", developed in the third and fourth chapters. This represents the beginning of the Strength of Materials as a science.

It is necessary to clarified that Galileo's approaches did not have the weight of a structured theory, but it was a guide to the researchers and scientists who succeeded him, so for example and in chronological order after Galileo arrived, Euler (1707-1783), Coulomb ( 1736-1806), Poisson (1781-1840), Navier (1785-1836), Cauchy (1789- 1857), and Airy (1801-1892) among others, who laid the foundation for the theory of the Strength of Materials. Theoretical bases that govern the structural design, which today allows us to have homes, machines, and equipment with greater degrees of reliability in its design, which make the life of today's man more comfortable.

The development of Strength of Materials, the application of mathematics, and the help of computers, has allowed for the creation of advanced techniques in the determination of stresses and strain on structural elements, under different conditions of load, temperature, etc., in a few minutes and even seconds.

The book Strength of Materials contains eleven peer-reviewed chapters organized in two sections. Section 1 is focused on the strength of metal and composites materials, in other words on traditional materials used in engineering projects. Chapter 1 predicted the tensile strengths of unidirectionally aligned carbon-fiber-reinforced plastic (UD-CFRP) using a spring element model. The model takes into account a stress concentration acting on an intact fiber surface from a fracture site in a neighboring fiber. The surface stress concentration was experimentally investigated by implementing multi-fiber fragmentation testing in combination with the spring element model simulation. On the other hand, Chapter 2 reviews the research history and status quo of the hardbanding materials in tool joints. The authors show the advantages and disadvantages of several kinds of wear-resisting materials.

Chapter 3 presents the study on the microstructural features, fracture toughness, and delamination occurrence of two X80 grade steel plates with different processing routes and chemical composition. A schematic model was proposed, showing the source of delamination and the reason for the lowest toughness for 45° to the rolling direction. Chapter 4 compares the classic static strength theory and fatigue strength theory of materials; due to the static contact strength being the limiting condition of contact fatigue strength.

Chapter 5 justifies the application of the aluminum-copper-lithium alloy 2050-T84 as a structural component of aircrafts, substituting aluminum alloys used at the present time, due to the possibility of reduction of density, an increase of stiffness, high fracture toughness, greater resistance to the propagation of cracks by fatigue, and greater resistance to corrosion. Chapter 6 studies the fatigue behavior of two generic components; a classical structure and a structure-mechanism, using three different methods of calculation; load history (static), transient modal superposition (dynamic), and frequency domain modal superposition (dynamic). The objective was to demonstrate the differences between each calculation methodology due to the different ways each considers the dynamic effect.

Finally, Section 1 ends with Chapter 7. This chapter analyzes the recent advances in the development of a modified hyperbolic sine law able to depict the minimum creep strain rate over a wider range of stress levels; the development of the creep fracture criterion and model based on the cavity area fraction along grain boundary calibrated with the most representative and comprehensive cavitation data obtained from x-ray synchrotron investigation, and the development of the mesoscopic composite approach modeling of creep deformation and creep damage.

Section 2 contains chapters on the strength of sustainable materials or non-conventional materials. Chapter 8 describes the evaluation and simulation of the mechanical behavior of bike-frames made out of bamboo. Included are some technical values of bamboo bike-frames and these will allow them to define the technical characteristics of the product and guarantee their operating conditions.

This is followed by Chapter 9, which assessed the use of self-healing technology on concrete using sustainable material as an active method of healing cracks, in order to improve the stability, strength, and sustainability of civil infrastructure. The outcome of the review showed three prominent methods used in self-healing technology, which include autogenous healing, encapsulation of polymeric material, and microbial production of calcium-carbonate (biotechnological approaches). The review also revealed that calcium carbonate is a versatile material that can be used in crack healing for the filling of voids and improve the porosity of the concrete.

Chapter 10 reviews the theoretical framework of nanomodification principles of building composites and experimental verification of these principles and, the concepts of nanomodification of building composite structures. The chapter also suggests the conceptual model of the nanomodification from the point of view of the evolutionary model of a solid phase formation depending on the kinetics of heterogeneous processes.

Section 2 and the book are closed with Chapter 11, which describes the research started with a laboratory-scale trial mix, using a Low Heat Concrete Bioconc based concrete Job Mix, from cement content reduction 20%, 25%, 30%, and 40%. The result showed the optimum job mix to be Low Heat Concrete Bioconc based concrete Job Mix on 40% cement as binder content reduction.

The eleven chapters in this book each focus on a particular aspect of the Strength of Materials, but are able to provide a general idea of the direction of current efforts on the use of Strength of Materials as a science. Within each chapter, the reader will come into contact not only with different topics in Strength of Materials, but also with several techniques of synthesis, characterization, and interpretation of results, which can be useful to synthesize and investigate other materials.

Dear reader, with this book you will have access to important subjects on the engineering and Strength of Materials. Chapters can be read in sequence as they are presented or in any sequence that the reader deems appropriate, due to each chapter being independent of the others. This is an excellent book that contains several recent topics at the frontier of knowledge on Strength of Materials, which can be consulted not only by experienced researchers but also by students to understand how vast this science can be.

### **Dr Héctor Enrique Jaramillo Suárez**

Science and Engineering of Materials Research Group, Energetic and Mechanical Department, Engineering Faculty, Autónoma de Occidente University, Cali, Colombia
